Vaccine Acronyms & Terms Glossary

A

AAP

The American Academy of Pediatrics is the principal professional organization representing pediatricians in the United States. Its policy statements and clinical guidance are frequently referenced in vaccine-related discussions and pediatric care standards.

ACCV

The Advisory Commission on Childhood Vaccines is a federally chartered body that provides recommendations to the Secretary of Health and Human Services on matters related to the operation of the Vaccine Injury Compensation Program.

ACIP

The Advisory Committee on Immunization Practices is a panel of medical and public health experts convened by the CDC to formulate recommendations on the use of vaccines in the civilian population of the United States.

Active immunity

A form of immune protection that develops when the body encounters a pathogen or receives a vaccine and mounts its own antibody response. This type of immunity can arise naturally through infection or be induced artificially through immunization, and it generally provides longer-lasting protection than passive immunity.

Adjuvant

A compound incorporated into certain vaccine formulations to strengthen and prolong the recipient's immune response. Aluminum-based compounds such as aluminum phosphate and aluminum hydroxide are among the most commonly used adjuvants worldwide. Other formulations include oil-in-water emulsions and newer compounds such as CpG 1018, a synthetic oligonucleotide developed for use in hepatitis B vaccines. Proprietary aluminum adjuvants, including amorphous aluminum hydroxyphosphate sulfate, are also used in specific licensed products.

Adsorbed

In pharmaceutical and vaccine manufacturing, adsorption refers to the process by which molecules in a liquid phase bind to and accumulate on a solid surface, such as when antigens attach to an adjuvant particle.

AE

An adverse event is any undesirable medical occurrence that takes place after the administration of a vaccine or pharmaceutical product, regardless of whether a causal link to the product has been established.

AEFI

Any unfavorable medical occurrence observed after a vaccination, whether or not it is causally related to the vaccine itself. Such events can range from minor symptoms to serious conditions including hospitalization or death. The Brighton Collaboration, working alongside the WHO and CIOMS, develops standardized case definitions and diagnostic criteria for classifying these events internationally.

AESI

An adverse event of special interest is a medically significant event that has been pre-identified by regulators, researchers, or trial sponsors for heightened monitoring due to its potential relevance to the safety profile of a particular vaccine or drug.

AMA

The American Medical Association is one of the largest physician organizations in the United States and is periodically referenced in discussions of vaccine policy, medical ethics, and professional clinical standards.

Antibody

A specialized protein, also known as an immunoglobulin, that the immune system generates in response to the detection of a foreign substance (antigen). Antibodies bind specifically to their target antigens and play a central role in the body's adaptive immune defense.

Antigen

Any substance capable of provoking an immune response in the body, including toxins, viral particles, bacteria, and foreign cells. In vaccine design, antigens serve as the primary component that stimulates the recipient's immune system to build protective defenses.

Antiserum

A preparation derived from blood serum that contains specific antibodies directed against a particular infectious agent or toxin. Antiserum is used to confer passive immunity, providing immediate but temporary protection against diseases such as diphtheria, tetanus, or venomous bites.

Antitoxins

Concentrated antibody preparations obtained from the blood of animals (most often horses) that have been repeatedly immunized with a specific toxin. The resulting antiserum is extracted and refined for use in humans, providing rapid passive immunity against toxin-mediated diseases such as diphtheria.

AR

An adverse reaction is a subset of adverse events for which available evidence suggests at least a plausible causal connection between the medical product administered and the clinical outcome observed.

ASD

Autism Spectrum Disorder is a neurodevelopmental condition that was the central subject of the Omnibus Autism Proceeding, a series of coordinated test cases adjudicated in the U.S. Court of Federal Claims under the VICP.

Attenuation

A laboratory technique used to reduce the disease-causing capacity of a pathogen while preserving its ability to stimulate an immune response. Viruses and bacteria can be attenuated through methods including serial passage in cell culture, chemical treatment, or controlled heat exposure, enabling their use in live vaccines.

B

Bacillus

A category of bacteria characterized by their elongated, rod-like shape. The term appears frequently in vaccine-related contexts, most notably in Bacillus Calmette-Guerin (BCG), the tuberculosis vaccine.

Bacterins

An early class of vaccines composed of whole bacterial organisms that have been killed, rendering them unable to cause disease while retaining their capacity to provoke an immune response. This approach was widely employed in vaccination programs during the early twentieth century.

BCG

Bacillus Calmette-Guerin is a live attenuated vaccine derived from Mycobacterium bovis, used primarily for the prevention of tuberculosis. While not part of the routine immunization schedule in the United States, BCG is widely administered in countries where tuberculosis remains endemic and appears in international vaccination comparisons.

Bioinformatics

An interdisciplinary field that applies computational tools and statistical methods to the analysis of biological data. Drawing on biology, computer science, mathematics, and information engineering, bioinformatics has become integral to vaccine research, genomic surveillance, and pathogen characterization. The analytical phase of this work is often referred to as computational biology.

Biologic

A category of medical products derived from living organisms or their cellular components, encompassing vaccines, antitoxins, blood-derived products, and other immunostimulatory preparations. In the United States, biologics are regulated through the FDA's Center for Biologics Evaluation and Research and are approved via the Biologics License Application pathway.

Biological weapon

An instrument of warfare that employs pathogenic organisms, toxins, or other biological agents — whether naturally occurring or engineered — to inflict harm on humans, animals, or agricultural systems. Biodefense considerations have historically influenced the development of vaccines against agents such as anthrax and smallpox.

BLA

A Biologics License Application is the regulatory submission that a manufacturer files with the FDA to obtain approval for a biological product, including vaccines. The BLA process is distinct from the New Drug Application pathway used for conventional pharmaceutical drugs.

C

CAFC

The Court of Appeals for the Federal Circuit is the appellate tribunal that hears appeals from the U.S. Court of Federal Claims, including challenges to decisions rendered by Special Masters in VICP proceedings.

Carcinogen

Any agent, chemical compound, or environmental factor capable of inducing cancer through mechanisms such as direct DNA damage, disruption of cellular metabolism, or promotion of uncontrolled cell growth.

CBER

The Center for Biologics Evaluation and Research is the division within the FDA responsible for the regulation and oversight of biological products, including vaccines, blood products, and gene therapy products.

CBRN

An abbreviation for Chemical, Biological, Radiological, and Nuclear threats, used within the FDA's regulatory framework for emergency use authorization of medical countermeasures in response to national security and public health emergencies.

CDC

The Centers for Disease Control and Prevention is the primary public health agency of the United States federal government, responsible for issuing immunization guidance, maintaining official vaccine abbreviation standards, and conducting disease surveillance programs.

CDSi

Clinical Decision Support for Immunization refers to CDC-developed systems and logic that help clinicians and immunization information systems determine which vaccines a patient is due for based on age, medical history, and prior doses received.

Chimeric

Derived from the Greek mythological creature, this term describes biological constructs composed of genetic or cellular material from two or more distinct organisms. In medical and research contexts, chimeric constructs include engineered proteins, cells, or tissues combining elements from different species or genetic backgrounds.

CICP

The Countermeasures Injury Compensation Program is a federal program administered by HRSA that provides compensation for injuries directly caused by the administration of covered countermeasures during declared public health emergencies, operating separately from the VICP.

CISA

The Clinical Immunization Safety Assessment Project is a collaborative network between the CDC and academic medical centers that offers specialized expert consultation for clinicians managing patients with complex vaccine safety questions.

Corporate Integrity Agreement

A compliance document executed between a healthcare company and a federal agency, typically HHS, as a condition of settling civil enforcement actions. These agreements generally impose a structured set of reporting, auditing, and compliance obligations over a five-year period.

CRADA

A Cooperative Research and Development Agreement is a legal mechanism that enables a federal laboratory — such as those operated by NIH, NIAID, or the Department of Defense — to enter into formal research partnerships with private-sector entities, including pharmaceutical manufacturers, to advance product development and technology transfer.

CRISPR-Cas9

A molecular tool that enables targeted modification of DNA sequences in living organisms by using the Cas9 enzyme to cut genetic material at specified locations. Originally adapted from a bacterial immune defense mechanism, CRISPR-Cas9 has broad applications in biomedical research, including potential uses in gene therapy and vaccine platform development. Concerns have also been raised about its potential misuse in the creation of engineered biological threats.

CRM197

A non-toxic variant of diphtheria toxin produced through genetic modification, widely employed as a carrier protein in conjugate vaccine formulations. First introduced commercially in the Hib vaccine HibTITER (approved in the U.S. in 1990), CRM197 is also used in several pneumococcal and meningococcal conjugate vaccines currently in use.

CVX

Vaccine Administered Codes are a standardized coding system maintained by the CDC for use in immunization information systems and electronic health records to consistently identify and track specific vaccine products.

D

DDT

Dichloro-diphenyltrichloroethane, a synthetic organochlorine pesticide widely deployed from the 1940s onward for vector control against insects carrying diseases such as typhus, malaria, and polio. Regulatory authorities in the United States and Canada prohibited its domestic use in 1972, and most European countries subsequently followed. DDT continues to be utilized in certain tropical and developing regions for malaria prevention programs.

DNA / RNA

The two primary types of nucleic acid molecules responsible for storing and transmitting genetic information in living organisms. DNA (deoxyribonucleic acid) serves as the long-term repository of hereditary instructions, while RNA (ribonucleic acid) functions as an intermediary that translates those instructions into functional proteins. Both molecules are composed of chains of nucleotides built from four bases — adenine, guanine, cytosine, and either thymine (in DNA) or uracil (in RNA).

DTaP

The standard abbreviation for the combination vaccine protecting against diphtheria, tetanus, and pertussis using an acellular pertussis component, administered to children in the current U.S. immunization schedule.

DTP / DTwP

An older vaccine formulation combining diphtheria and tetanus toxoids with a whole-cell pertussis component. This abbreviation persists in historical records, older medical literature, and VICP case documentation, though the vaccine has been replaced by acellular formulations (DTaP) in the United States.

DVIC

The Division of Vaccine Injury Compensation is the organizational unit within HRSA charged with the day-to-day administration of the Vaccine Injury Compensation Program.

E

EBCALA

The Elizabeth Birt Center for Autism Law and Advocacy is an organization that has been involved in vaccine-related legal proceedings and is referenced in litigation materials associated with the U.S. Court of Federal Claims.

Efficacy v. Effectiveness

Two related but distinct measures of vaccine performance. Efficacy quantifies a vaccine's ability to prevent disease under the controlled conditions of a clinical trial, typically comparing vaccinated participants against a placebo group. Effectiveness, by contrast, measures real-world performance, accounting for variables such as population diversity, storage conditions, and varying administration practices that clinical trials may not fully capture.

Encephalitis

An inflammatory condition of the brain, most commonly triggered by viral infection. Encephalitis is listed as a recognized injury on the Vaccine Injury Table for certain covered vaccines under the VICP.

Encephalopathy

A broad clinical term for disease or dysfunction of the brain resulting from neuronal damage. Like encephalitis, encephalopathy appears on the Vaccine Injury Table as a compensable condition associated with certain vaccines.

Epidemic

A notable and often rapid increase in the number of cases of a disease within a defined population or geographic area over a specific time period. The term is generally applied to outbreaks confined within a single country or region, as distinct from pandemics, which cross international boundaries.

Epidemiology

The scientific discipline concerned with analyzing patterns, causes, and effects of disease within populations. Epidemiological methods are foundational to public health practice and inform vaccine policy decisions, though the field's observational nature means that its studies can identify associations but are generally not sufficient on their own to establish definitive causation.

EPI

The Expanded Programme on Immunization is a WHO-coordinated initiative established in 1974 to ensure that all children worldwide have access to recommended vaccines, particularly in low- and middle-income countries.

Escherichia coli

A gram-negative, rod-shaped bacterium that thrives in both aerobic and anaerobic conditions. Beyond its well-known role in gastrointestinal health and disease, E. coli has become one of the most widely used organisms in biotechnology for the production of recombinant vaccine antigens, including engineered toxins and viral peptides.

EUA

An Emergency Use Authorization is a regulatory mechanism through which the FDA can permit the distribution and use of medical products — including vaccines, therapeutics, and diagnostics — during qualifying public health emergencies, prior to the completion of full licensure review.

F

FACA

The Federal Advisory Committee Act is the statute that governs the formation and operation of advisory committees within the federal government, including bodies such as ACIP and ACCV that play key roles in vaccine policy.

FDA

The Food and Drug Administration is the federal agency with jurisdiction over the approval, authorization, labeling, manufacturing standards, and post-market oversight of vaccines and other medical products in the United States.

FOIA

The Freedom of Information Act is a federal statute that grants members of the public the right to request access to records held by executive branch agencies, subject to certain exemptions for classified, proprietary, or privacy-protected information.

G

Gain-of-function

A category of laboratory research in which scientists deliberately modify a microorganism to enhance specific biological capabilities, such as its transmissibility between hosts or its virulence. Proponents contend that such work is necessary for anticipating emerging pandemic threats and developing countermeasures, while critics argue that it poses unacceptable biosafety and biosecurity risks. The practice became a prominent subject of public policy debate during and after the COVID-19 pandemic.

GAO

The Government Accountability Office is the investigative and auditing arm of the U.S. Congress, responsible for evaluating federal programs and expenditures. GAO reports are frequently cited in discussions of vaccine program oversight, Trust Fund management, and federal policy review.

GBS

Guillain-Barre Syndrome is an uncommon neurological disorder in which the body's immune system attacks peripheral nerves. GBS appears in vaccine safety literature and is listed on portions of the HRSA Vaccine Injury Table as a recognized condition associated with certain covered vaccines, particularly seasonal influenza.

Genome

The complete collection of genetic material contained within an organism, encoded in sequences of DNA (or RNA in certain viruses). In humans, the genome spans approximately 3 billion base pairs organized across 23 pairs of chromosomes, with protein-coding sequences representing roughly 2% of the total.

Gram-negative / positive

A foundational bacteriological classification system introduced by Danish microbiologist Hans Christian Gram in 1884. The technique uses a crystal violet staining procedure to differentiate bacteria based on cell wall composition: gram-positive organisms retain the stain (indicating thicker cell walls), while gram-negative organisms do not. This distinction has practical significance for antibiotic selection, as drug resistance disproportionately affects gram-negative species.

H

hCG (Human chorionic gonadotropin)

A peptide hormone produced by trophoblast cells during early pregnancy that signals the maternal body to sustain the developing embryo. Following implantation, these cells eventually form the placenta. The hormone is widely used as a marker in pregnancy testing and has been referenced in international vaccine controversies involving allegations of anti-fertility agents.

Hemagglutinin

A class of glycoprotein molecules found on the surface of influenza viruses that facilitate viral attachment to host cells by binding to sialic acid residues, causing red blood cells to aggregate. Sixteen distinct hemagglutinin subtypes (H1 through H16) have been identified and are used in combination with neuraminidase subtypes to classify influenza A viruses (e.g., H1N1, H5N1).

Hep B

The standard abbreviated reference for the hepatitis B vaccine or the broader hepatitis B vaccine product category, depending on context.

Herd immunity

Sometimes referred to as community immunity, this concept holds that when a sufficiently large proportion of a population is immune to a given disease, even unvaccinated individuals receive indirect protection because the pathogen has fewer opportunities to spread. The required threshold varies by disease; for highly contagious measles, estimates have risen from approximately 55-60% in the 1960s to around 95% in current modeling. Whether vaccination alone can achieve herd immunity for certain diseases — including tetanus, diphtheria, influenza, COVID-19, polio, and pertussis — remains a subject of scientific discussion, particularly given differences in how individual vaccines affect transmission versus disease severity.

HHS

The U.S. Department of Health and Human Services is the federal cabinet-level department that encompasses major health-related agencies including the CDC, FDA, NIH, and HRSA.

Hib

The abbreviation for the Haemophilus influenzae type b conjugate vaccine, which protects against invasive bacterial infections caused by H. influenzae type b, including meningitis and pneumonia in young children.

HPV

The abbreviation for Human Papillomavirus vaccines, which protect against strains of HPV associated with cervical and other cancers as well as genital warts.

HRSA

The Health Resources and Services Administration is an agency within HHS headquartered in North Bethesda, Maryland, that administers both the VICP and the CICP. Beyond vaccine compensation programs, HRSA's broader mission centers on expanding healthcare access for underserved, uninsured, and medically vulnerable populations.

I

ICAN

The Informed Consent Action Network is an advocacy organization that engages in public discourse on vaccine policy, transparency, and individual choice. It appears in vaccine-related legal filings and public debate.

IIS

An Immunization Information System is a confidential, population-level electronic database operated by a public health jurisdiction to record and track vaccine doses administered to individuals within its geographic area.

IIV

The abbreviation for Inactivated Influenza Vaccine, a category of seasonal flu vaccines produced using killed virus particles.

Immunity

The state of biological protection against a specific infectious disease, achieved either through prior natural infection, vaccination, or the transfer of protective antibodies from another source.

Immunization

The process by which an individual acquires protection against a specific disease, typically through the administration of a vaccine. The resulting state of immune readiness is also referred to as immunization.

Immunization vs. Vaccination

Although commonly used as interchangeable terms, immunization and vaccination carry distinct meanings. Vaccination refers specifically to the act of administering a vaccine, while immunization describes the broader outcome — the development of immune protection — which may or may not result from vaccination.

In silico

A term describing research activities performed entirely through computational methods, including computer modeling, simulation, and bioinformatics analysis. This approach is distinguished from in vitro studies (conducted in laboratory vessels) and in vivo studies (conducted in living organisms).

IND

An Investigational New Drug application is the regulatory submission filed with the FDA to obtain authorization for administering an experimental product to human subjects during clinical trials.

Influenza

An acute respiratory infection caused by influenza viruses, primarily types A and B. Type A viruses are classified into subtypes based on two surface proteins — hemagglutinin and neuraminidase — producing designations such as H1N1 and H5N1. Type B viruses are divided into two principal lineages (Yamagata and Victoria). Seasonal influenza vaccines are reformulated annually and typically contain multiple virus strains; trivalent and quadrivalent formulations include at least one type B component alongside type A subtypes.

Inoculation

The deliberate introduction of an antigenic material into the body for the purpose of stimulating an immune response and conferring protection against a specific disease. In contemporary usage, the term is largely synonymous with vaccination.

IOM

The Institute of Medicine was the former designation of what is now the National Academy of Medicine. Its earlier reports and consensus studies on vaccine safety continue to be widely cited in scientific and legal literature.

IPV

The abbreviation for Inactivated Poliovirus Vaccine, the injectable Salk-type polio vaccine that is the standard formulation used in the current U.S. immunization schedule.

J

No current core glossary entries.

K

No current core glossary entries.

L

LAIV

The abbreviation for Live Attenuated Influenza Vaccine, a nasally administered seasonal flu vaccine produced using weakened live virus strains.

Lipid nanoparticles

Microscopic particles composed of lipid (fat-based) molecules that serve as delivery vehicles for pharmaceutical agents, including messenger RNA. Typically ranging from 1 to 500 nanometers in diameter, lipid nanoparticles protect their molecular cargo from degradation and facilitate cellular uptake. They became widely recognized as a critical enabling technology in mRNA-based COVID-19 vaccine platforms.

Liposomes

Artificially constructed spherical vesicles made from layers of cholesterol and phospholipid molecules. Their structure allows them to encapsulate and transport pharmaceutical compounds, including vaccine antigens, to target cells in the body.

M

MAAE

A Medically Attended Adverse Event is an adverse event of sufficient clinical significance that it results in a visit to a healthcare provider, emergency department, or other medical facility.

Mathematical models

Computational frameworks that use simplified representations of complex biological and social phenomena to simulate potential real-world outcomes. In infectious disease epidemiology, mathematical models inform public health decision-making across areas including emergency preparedness, economic impact analysis, and vaccination strategy. Prominent modeling centers, including Imperial College London, have played influential roles in shaping governmental responses to disease outbreaks, including during the COVID-19 pandemic. The reliability and assumptions underlying these models remain subjects of ongoing scientific and policy debate.

MCM

Medical Countermeasure is the FDA's umbrella classification for products — including vaccines, drugs, biologics, diagnostics, and medical devices — that may be deployed in response to chemical, biological, radiological, nuclear, or emerging infectious disease threats.

MedDRA

The Medical Dictionary for Regulatory Activities is an internationally standardized clinical terminology system developed by the International Council for Harmonisation (ICH). Regulatory agencies and pharmaceutical companies use MedDRA for the systematic classification, coding, and retrieval of adverse event data throughout the product lifecycle, from pre-market clinical trials through post-market surveillance.

MenABCWY

The abbreviation for a pentavalent meningococcal vaccine providing protection against serogroups A, B, C, W, and Y of Neisseria meningitidis.

MenACWY

The abbreviation for a quadrivalent meningococcal vaccine covering serogroups A, C, W, and Y.

MenB

The abbreviation for a meningococcal serogroup B vaccine, targeting the B serogroup of Neisseria meningitidis.

Metagenomics

A genomic research methodology that enables scientists to analyze the collective DNA of microbial communities sampled from environmental or biological sources, bypassing the need for traditional organism isolation and culture. Viral metagenomics in particular has expanded the ability to detect and characterize previously unrecognized viruses.

MMR

The abbreviation for the combined vaccine providing protection against measles, mumps, and rubella.

MMRV

The abbreviation for the combination vaccine covering measles, mumps, rubella, and varicella (chickenpox) in a single administration.

MMWR

The Morbidity and Mortality Weekly Report is the CDC's flagship publication series, used to disseminate vaccine recommendations, epidemiological findings, and public health guidance to clinicians and health officials.

Monoclonal antibodies (mAbs)

Laboratory-manufactured proteins engineered to mimic the immune system's ability to target specific antigens. Each monoclonal antibody is derived from a single cloned B cell lineage, ensuring uniform specificity. Originally developed for therapeutic applications in oncology and autoimmune disease, monoclonal antibodies have more recently been deployed as preventive immunizing agents, including RSV-specific products for infants.

Mutagenic

Describing any agent, chemical, or physical process capable of inducing changes to an organism's DNA sequence. Mutagenic alterations may be permanent and heritable, with potential consequences ranging from neutral to pathological.

N

Nanotechnology

The engineering discipline focused on designing and fabricating materials, devices, and systems at the molecular and atomic scale, generally defined as structures with at least one dimension measuring 100 nanometers or less. The concept was first articulated by physicist Richard Feynman in 1959, and the term itself was coined by Japanese scientist Norio Taniguchi. In vaccine science, nanotechnology underpins the development of lipid nanoparticle delivery systems used in mRNA vaccine platforms.

NCVIA

The National Childhood Vaccine Injury Act of 1986 is the federal statute that established the VICP, created the Office of Special Masters within the U.S. Court of Federal Claims, and mandated the distribution of Vaccine Information Statements to recipients prior to immunization.

NDA

A New Drug Application is the regulatory pathway through which conventional pharmaceutical drugs (as opposed to biologics) are submitted to the FDA for market approval. The distinction between the NDA and BLA pathways is relevant for understanding how different categories of medical products are regulated.

Neuraminidase

A surface enzyme found on influenza viruses that facilitates the release of newly formed viral particles from infected host cells. Together with hemagglutinin, neuraminidase serves as one of the two key antigens used to classify influenza A subtypes in the standard H/N naming convention.

New chemical / molecular entity

Regulatory terms used to describe novel products undergoing initial FDA review. A new chemical entity (NCE) refers specifically to a small-molecule drug not previously approved. A new molecular entity (NME) is a broader designation that includes both chemical and biological innovations, encompassing the antigens used in new vaccine candidates.

NIH

The National Institutes of Health is the primary biomedical research institution of the United States federal government. NIH-funded research is extensively cited in vaccine development, immunology studies, and public health policy discussions.

NPRM

A Notice of Proposed Rulemaking is a formal announcement published in the Federal Register through which a federal agency signals its intent to create or modify regulations, inviting public comment before finalization.

Nucleic acid

A class of large biological molecules — principally DNA and RNA — composed of chains of nucleotide subunits. Nucleic acids are responsible for encoding, transmitting, and expressing genetic information in all known cellular organisms and many viruses.

Nucleotide

The fundamental building block of nucleic acids, each consisting of three components: a five-carbon sugar (ribose in RNA, deoxyribose in DNA), a phosphate group, and one of four nitrogen-containing bases. In DNA, the bases are adenine (A), cytosine (C), guanine (G), and thymine (T); RNA substitutes uracil (U) for thymine.

O

OAP

The Omnibus Autism Proceeding was a consolidated legal action within the VICP in which the U.S. Court of Federal Claims evaluated representative test cases alleging that vaccines caused autism spectrum disorder. The proceeding resulted in rulings against the petitioners in all test cases.

One Health

A collaborative public health framework, formally conceptualized in 2006, that recognizes the interdependence of human health, animal health, and environmental conditions. Currently coordinated by the FAO, UNEP, WHO, and WOAH, the One Health approach is applied to challenges including zoonotic disease surveillance, antimicrobial resistance, and pandemic preparedness.

OPV

Oral Poliovirus Vaccine, developed by Albert Sabin, was the primary polio vaccine used in the United States for decades before being replaced by the inactivated formulation (IPV). OPV continues to appear in historical VICP claims data and remains in use in some global eradication campaigns.

OSM

The Office of Special Masters is the specialized adjudicative body within the U.S. Court of Federal Claims that is responsible for hearing and deciding petitions filed under the VICP.

P

PACER

Public Access to Court Electronic Records is the federal judiciary's online system for retrieving case filings, docket information, and court documents, including records from VICP proceedings in the U.S. Court of Federal Claims.

Palindromic sequence

A segment of double-stranded DNA or RNA in which the nucleotide sequence reads identically in the same direction on both complementary strands. Palindromic sequences are significant in molecular biology as recognition sites for restriction enzymes and are referenced in the naming of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) gene-editing technology.

Pandemic

An outbreak of infectious disease that spreads across multiple countries or continents, exceeding the geographic scope of an epidemic. Major pandemics in history include the 1918 influenza outbreak and the COVID-19 pandemic beginning in 2019.

Passive immunity

Immune protection obtained through the transfer of pre-formed antibodies from one individual to another, rather than through the recipient's own immune response. Examples include maternal antibodies passed to a newborn during pregnancy or breastfeeding, and therapeutic antiserum preparations. Passive immunity takes effect immediately but is temporary, typically lasting only weeks to months.

PCV

Pneumococcal Conjugate Vaccine, a vaccine category that protects against infections caused by Streptococcus pneumoniae. Current CDC guidance specifies formulations by valency, including PCV15, PCV20, and PCV21.

PCV15 / PCV20 / PCV21

Designations for 15-valent, 20-valent, and 21-valent pneumococcal conjugate vaccine formulations, reflecting the number of pneumococcal serotypes covered by each product.

Pharmacodynamics

The branch of pharmacology concerned with understanding how drugs and other bioactive substances affect the body's biological processes at the molecular, cellular, and systemic levels. Because vaccines function through immune mechanisms rather than conventional pharmacological pathways, traditional pharmacodynamic studies are not a standard component of vaccine regulatory submissions.

Pharmacokinetics

The study of how drugs are absorbed, distributed, metabolized, and eliminated by the body over time. Because vaccines operate by stimulating the immune system rather than maintaining sustained drug concentrations in the bloodstream, conventional pharmacokinetic studies are generally not a standard regulatory requirement for vaccine licensure.

Pharmacovigilance

The systematic science of monitoring, detecting, evaluating, and preventing adverse effects associated with vaccines and pharmaceutical products after they enter the market. The WHO defines vaccine pharmacovigilance as encompassing both the identification of adverse events following immunization and the broader assessment of vaccine- or immunization-related safety concerns. Pharmacovigilance activities draw on data from spontaneous reporting systems, active surveillance networks, and epidemiological studies to generate and investigate safety signals.

Plasmid

A small, circular segment of DNA found naturally in bacteria and yeast that replicates independently of the organism's chromosomal DNA. Plasmids are a foundational tool in genetic engineering and are widely used in vaccine research and production as vectors for inserting and expressing foreign genes.

POI

Primary Ovarian Insufficiency is a medical condition characterized by the loss of normal ovarian function before age 40. The abbreviation appears in certain vaccine injury claim filings and case discussions.

Polymerase Chain Reaction (PCR)

A laboratory technique developed by Kary Mullis in 1983 that enables the rapid amplification of specific DNA sequences, generating billions of copies from a minimal starting sample. PCR is used extensively in pathogen detection, genetic testing, and forensic analysis. Its role as a diagnostic tool has been a subject of discussion, particularly regarding the distinction between detecting genetic material and confirming active clinical disease.

PPSV23

The abbreviation for the 23-valent pneumococcal polysaccharide vaccine, which provides coverage against 23 serotypes of Streptococcus pneumoniae.

PREP Act

The Public Readiness and Emergency Preparedness Act is a federal statute that provides liability protections for manufacturers, distributors, and administrators of covered countermeasures during declared public health emergencies. Injury claims related to covered countermeasures are directed to the CICP rather than the VICP or civil courts.

PRISM

The Post-licensure Rapid Immunization Safety Monitoring program is a federal vaccine safety surveillance initiative that analyzes administrative claims data from large health insurance databases to detect potential safety signals associated with newly licensed or widely administered vaccines.

Product Development Partnership (PDP)

A category of public-private collaboration established to accelerate the development of health products — particularly vaccines, therapeutics, and diagnostics — for diseases that disproportionately affect low-income populations and lack sufficient commercial incentive for private-sector investment. The PDP model traces its origins to a 1994 Rockefeller Foundation conference focused on HIV vaccine development.

Proteins

Complex biological molecules composed of amino acid chains that perform essential functions throughout the body, including enzymatic catalysis, immune defense (as antibodies), hormonal signaling, and structural support for cells and tissues. Protein-based antigens are central components of many vaccine formulations.

PSC

The Petitioners' Steering Committee is an organizational structure used in coordinated vaccine litigation proceedings, most notably in the Omnibus Autism Proceeding, to manage and present claims on behalf of large groups of petitioners.

Public-Private Partnership (PPP)

A structured collaboration between governmental or international public institutions and private commercial entities, designed to combine public resources and regulatory capacity with private-sector capital, expertise, and manufacturing capability. In the vaccine field, PPPs have been used to advance product development and distribution for diseases including HIV, malaria, and tuberculosis.

Q

QAI

Qualifications and Aids to Interpretation is the supplementary explanatory framework published alongside the Vaccine Injury Table, providing guidance on how to apply the Table's criteria when evaluating whether a petitioner's injury meets the requirements for presumptive causation under the VICP.

R

RCFC

The Rules of the Court of Federal Claims are the procedural rules governing litigation in the U.S. Court of Federal Claims, including the specialized procedures applicable to VICP vaccine injury petitions.

Recombinant

A term describing biological material — typically DNA, RNA, or proteins — that has been engineered in a laboratory by combining genetic sequences from two or more different organisms. Recombinant technology is a cornerstone of modern vaccine manufacturing.

Recombinant DNA (rDNA)

DNA molecules constructed through laboratory genetic engineering techniques that join genetic sequences from multiple biological sources into combinations not found in nature. The process relies on restriction enzymes to cut DNA at precise locations and plasmid or viral vectors to carry the recombined material into host cells for replication.

Recombumin

A recombinant form of human serum albumin manufactured without the use of human or animal blood products. Produced from a genetically modified strain of the yeast Saccharomyces cerevisiae, it is used as a stabilizing excipient in certain vaccine formulations, including MMRVaxPro and IXCHIQ.

Replicons (viral RNA)

Self-amplifying RNA constructs engineered to carry the genetic instructions for their own replication machinery, but deliberately designed to be incapable of producing complete infectious virus particles. RNA replicon platforms are under active investigation as a next-generation approach to vaccine delivery, potentially offering stronger immune responses at lower doses than conventional mRNA vaccines.

Reverse vaccinology

A genome-based approach to vaccine antigen discovery, pioneered by Rino Rappuoli and colleagues at Chiron in 2000, that uses bioinformatics tools to systematically screen pathogen genomes for proteins likely to elicit strong immune responses. The methodology proved its value with the development of the meningococcal serogroup B vaccine Bexsero, which received regulatory approval in 2013.

RIV

The abbreviation for Recombinant Influenza Vaccine, a category of seasonal flu vaccines produced using recombinant DNA technology rather than egg-based or cell-based culture methods.

RSD

Residual Seizure Disorder is a clinical term that may appear in vaccine injury case records and VICP petition documentation in connection with seizure-related claims.

RSV

Respiratory Syncytial Virus is a common respiratory pathogen for which preventive vaccines have recently been incorporated into immunization guidance for certain populations, including older adults and pregnant individuals.

RSV-mAb

A monoclonal antibody product designed to provide passive immunization against respiratory syncytial virus. These products are tracked separately from traditional vaccines in CDC immunization schedules and recommendation frameworks.

RZV

The abbreviation for Recombinant Zoster Vaccine (marketed as Shingrix), the currently recommended vaccine for the prevention of shingles (herpes zoster) in adults.

S

SAE

A Serious Adverse Event is an adverse event that meets predefined regulatory criteria for severity, including outcomes such as death, life-threatening conditions, inpatient hospitalization, persistent disability, or congenital anomaly.

Safe

In everyday language, safety implies the absence of danger or risk. In the regulatory and medical context, however, safety is understood as a relative concept — a determination that the documented benefits of a product are judged by regulatory authorities to exceed its identified and potential risks, based on the available evidence at the time of evaluation.

SCDM

Shared Clinical Decision-Making is a recommendation category introduced in the CDC's 2026 three-tier immunization framework, applicable to vaccines for which the decision to immunize is made collaboratively between a clinician and individual patient based on personal risk factors, rather than being universally recommended for an entire population group.

SCN1A

A gene that encodes a sodium channel protein critical to neuronal function. Mutations in SCN1A are associated with several forms of epilepsy and have been discussed in vaccine-court proceedings concerning causation theories in seizure disorder cases.

Serum

The liquid component of blood remaining after cells and clotting factors have been removed. When collected from individuals or animals with immunity to a specific pathogen, serum containing protective antibodies (antiserum) can be administered to provide passive immunity to recipients.

SIDS

Sudden Infant Death Syndrome refers to the unexplained death of an apparently healthy infant under one year of age, typically during sleep, that remains unexplained after a thorough investigation including autopsy, review of clinical history, and examination of the death scene.

SIRVA

Shoulder Injury Related to Vaccine Administration is a recognized injury category on the HRSA Vaccine Injury Table, encompassing shoulder dysfunction resulting from the physical act of vaccine injection rather than from the vaccine's biological contents.

SM

A Special Master is a judicial officer appointed by the judges of the U.S. Court of Federal Claims to preside over and adjudicate individual vaccine injury petitions filed under the VICP.

SUID

Sudden Unexpected Infant Death is a broad classification encompassing all sudden and unexpected deaths of infants under one year, including SIDS, accidental suffocation in a sleep environment, and deaths from undetermined causes.

SV40

Simian Virus 40 is a polyomavirus originally identified in rhesus monkey kidney cell cultures that were used to manufacture early Salk and Sabin polio vaccines during the 1950s and early 1960s. An estimated 10 to 30 million Americans may have received contaminated vaccine during this period. SV40 has been shown to induce tumors in laboratory animals, including brain cancers, bone cancers, mesothelioma, and lymphomas. Whether SV40 causes disease in humans remains a contested question in the scientific literature, with some researchers describing evidence of human infection and others citing insufficient proof of a causal link to human cancers. The virus has also become an important tool in molecular biology research, notably in the development of the HEK293T cell line used for recombinant protein production.

T

Td

The abbreviation for the tetanus and diphtheria toxoid vaccine formulation used as a booster in adolescents and adults.

Tdap

The abbreviation for the tetanus, diphtheria, and acellular pertussis vaccine recommended for adolescents, adults, and pregnant individuals.

Teratogenic

Describing any agent, substance, or environmental exposure capable of causing structural or functional abnormalities in a developing embryo or fetus when encountered during pregnancy.

Thimerosal

An organomercury preservative compound containing approximately 49.6% ethylmercury by weight, used in multi-dose vaccine vials since 1929 to prevent bacterial and fungal contamination. A standard 0.01% thimerosal solution contains 25 micrograms of mercury per 0.5 mL dose. Beginning in 1999, thimerosal was removed from or reduced in most childhood vaccines in developed countries as a precautionary measure, with 2-phenoxyethanol and phenol serving as common replacements. Thimerosal continues to be used in multi-dose vaccine vials distributed in many developing nations. Some vaccines marketed as "thimerosal-free" may still contain residual amounts below 0.5 micrograms per dose. The WHO uses the term "thimerosal-reduced" to describe products containing 1-2 mcg/mL in the final formulation. The pharmacokinetics of ethylmercury in infants has not been comprehensively characterized in the published literature.

Toxoid

A modified bacterial toxin that has been rendered non-toxic through chemical treatment (typically with formalin) or heat inactivation while retaining its ability to stimulate the production of protective antibodies. Toxoid-based vaccines are used to prevent diseases such as diphtheria and tetanus.

Trace Amounts (vaccine ingredients)

Residual quantities of manufacturing process chemicals that remain in the final vaccine product at very low concentrations. The Institute of Medicine has defined trace amounts as less than 0.5 micrograms (500 nanograms) per dose, while the Institute for Vaccine Safety at Johns Hopkins University uses a threshold of less than 0.3 micrograms (300 nanograms). The biological significance of trace-level residual exposures, including questions about accumulation and interaction with metabolic pathways, continues to be evaluated as part of ongoing vaccine safety assessment.

U

No current core glossary entries.

V

VAERS

The Vaccine Adverse Event Reporting System is a national passive surveillance system co-managed by the CDC and FDA that accepts reports of adverse events occurring after vaccination from healthcare providers, manufacturers, and the public.

VAR

The abbreviation for the varicella (chickenpox) vaccine.

VFC

The Vaccines for Children program is a federally funded entitlement program that provides recommended vaccines at no cost to children who are Medicaid-eligible, uninsured, underinsured, or American Indian/Alaska Native, through participating enrolled providers.

VICP

The Vaccine Injury Compensation Program is the federal no-fault compensation system created by the NCVIA in 1986 to provide an administrative alternative to civil litigation for individuals alleging injury from covered vaccines.

VIS

A Vaccine Information Statement is a document produced by the CDC that describes the benefits and risks of a specific vaccine. Federal law requires that a current VIS be provided to the vaccine recipient or their parent/guardian before each dose of certain vaccines is administered.

VIT

The Vaccine Injury Table is the regulatory table maintained by HRSA that lists specific injuries, conditions, and time intervals presumptively associated with covered vaccines for purposes of VICP adjudication.

VRBPAC

The Vaccines and Related Biological Products Advisory Committee is an independent expert panel that advises the FDA on scientific and regulatory questions related to vaccine development, evaluation, and authorization.

VSD

The Vaccine Safety Datalink is a collaborative research and surveillance network linking the CDC with multiple integrated healthcare organizations to conduct population-based studies of vaccine safety using linked electronic health data.

W

WHO

The World Health Organization is the specialized health agency of the United Nations, responsible for coordinating international public health efforts including global immunization programs, vaccine safety terminology standards, and the classification of adverse events following immunization.

X

No current core glossary entries.

Y

YF

The abbreviation for Yellow Fever vaccine, a live attenuated immunization required for entry into certain countries in Africa and South America and included in the WHO's Expanded Programme on Immunization.

Z

No current core glossary entries.

Y

YF

The abbreviation for Yellow Fever vaccine, a live attenuated immunization required for entry into certain countries in Africa and South America and included in the WHO's Expanded Programme on Immunization.

Z

ZVL

Zoster Vaccine Live (formerly marketed as Zostavax) was the original shingles vaccine, using a live attenuated formulation of varicella-zoster virus. It has been supplanted by the recombinant zoster vaccine (RZV/Shingrix) and is no longer available for administration in the United States.

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