How often can you get a flu shot?

How Often Can You Get a Flu Shot

You should get a flu shot once every year, annually, regardless of whether the vaccine strains have changed from the previous season. 1, 2

Why Annual Vaccination is Required

Annual influenza vaccination is necessary for two critical reasons:

• Immunity wanes over time: Protection from the flu vaccine declines within the year following vaccination, making last year's shot insufficient for this year's protection 1, 2
• Virus strains change: The influenza virus undergoes constant mutation (antigenic drift), and vaccine composition is updated annually based on global surveillance to match circulating strains 1, 2, 3

Even when vaccine strains remain unchanged from the previous season, annual vaccination is still required because immunity naturally declines over the months following vaccination 1, 2

Optimal Timing for Annual Vaccination

For most people, get vaccinated in September or October to ensure protection before peak influenza season, which typically occurs in January through March 1, 4

Age-Specific Timing Considerations:

• Adults ≥65 years and pregnant persons (first/second trimester): Avoid July-August vaccination unless later vaccination may not be possible, to prevent immunity from waning before peak season 1, 4
• Pregnant persons (third trimester): Can consider July-August vaccination to provide passive protection to the infant during their first months of life when they're too young to be vaccinated 1
• Children 6 months-8 years requiring 2 doses: Start as early as possible (including July-August if available) to complete both doses by end of October 1, 4

Special Dosing Rules for Young Children

Children aged 6 months through 8 years have unique requirements that differ from the annual single-dose recommendation:

• First-time recipients: Require 2 doses separated by at least 4 weeks during their first season of vaccination 1, 5
• Previously vaccinated children: Need only 1 dose annually if they have received ≥2 total doses of influenza vaccine (trivalent or quadrivalent) at least 4 weeks apart before July 1 of the current season 1, 4
• Children with incomplete prior vaccination: If they received fewer than 2 total doses before July 1, they require 2 doses in the current season 1, 4

The two previous doses do not need to have been received during the same or consecutive seasons 1

Continue Vaccination Throughout the Season

Vaccination should continue as long as influenza viruses are circulating and unexpired vaccine is available, even after influenza activity has been documented in the community 1, 4, 6

Influenza season often extends well into March and beyond, with multiple peaks possible in a single season 1

Common Pitfalls to Avoid

• Don't skip vaccination thinking last year's shot still protects you: Immunity wanes significantly within 6 months, with studies showing odds of influenza infection increasing by approximately 16% for each additional 28 days since vaccination 7
• Don't wait too long in the season: While late vaccination is better than none, delaying until January or February means missing protection during early season activity 1, 4
• Don't assume vaccine ineffectiveness means you shouldn't get it: Even in seasons with reduced effectiveness against specific strains (like H3N2), vaccination still prevents serious outcomes including hospitalization and death 6, 8
• For children under 9 years: Don't forget the two-dose requirement for inadequately vaccinated children—incomplete vaccination leaves them unprotected during peak season 5, 2