A contagious respiratory illness caused by influenza viruses. Annual vaccination is the best way to prevent illness and serious complications.
Influenza (flu) is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs. It can cause mild to severe illness, and at times can lead to death. Annual influenza vaccination has been a longstanding public health strategy against seasonal flu. As of the January 2026 federal schedule reorganization, influenza vaccination for children is categorized under Shared Clinical Decision-Making (Tier 3), meaning the decision to vaccinate is based on individual consultation between patients or parents and their healthcare provider.
Flu seasons vary in timing, severity, and length. In the United States, flu activity typically peaks between December and February, but can last as late as May. The CDC estimates that flu has resulted in 9-41 million illnesses, 140,000-710,000 hospitalizations, and 12,000-52,000 deaths annually since 2010 (CDC, 2024).
Influenza viruses are constantly changing (antigenic drift), which is why new flu vaccines are developed each year. The WHO Global Influenza Surveillance and Response System (GISRS) monitors influenza viruses globally and recommends which strains should be included in flu vaccines for the upcoming season.
There are four types of influenza viruses: A, B, C, and D. Types A and B cause seasonal epidemics in humans. Influenza A viruses are further classified into subtypes based on surface proteins hemagglutinin (HA) and neuraminidase (NA), such as H1N1 and H3N2.
Vaccine effectiveness varies each year depending on how well the vaccine strains match circulating strains, the health and age of the recipient, and other factors. Effectiveness typically ranges from 30-60%.
Vaccination is a well-established strategy for reducing influenza illness and complications. Under the 2026 federal framework, influenza vaccination for children is recommended through shared clinical decision-making. The following describes established medical consensus for clinical management for those who contract infection.
Antiviral therapy with Oseltamivir (Tamiflu) or Baloxavir marboxil (Xofluza) reduces symptom duration and complication risk. Most effective when initiated within 48 hours of symptom onset. High-risk patients (elderly, immunocompromised, pregnant) should receive antivirals regardless of symptom onset timing. Supportive care includes rest and hydration. Avoid aspirin in children due to risk of Reye syndrome.
Disclaimer: This information is for educational purposes only. Treatment decisions must be made by a qualified healthcare provider.