What is the recommended frequency for seasonal influenza vaccination for adults?

• A. Every 12 months
• B. Every 2 years
• C. Every 3 years
• D. Every 5 years

Answer: (A)

Seasonal influenza vaccines are given every year because the virus changes year to year and immune protection from a prior vaccination doesn’t reliably cover the next season. Each year, vaccines are reformulated to target the strains expected to circulate, and the protective immune response from vaccination wanes over several months. That’s why adults are advised to receive the influenza vaccine annually, ideally before the flu season starts, to maintain optimal protection.

Vaccinating annually also helps reduce the risk of illness and complications in adults and aligns with public health recommendations. Receiving the vaccine once every several years would leave most people vulnerable during part of the season, since protection is not long-lasting and the circulating strains can differ from year to year. If you’ve already had a flu shot in the past, you should still get the current season’s vaccine.