Influenza Vaccination Frequency Recommendations
The influenza vaccine should be administered annually for optimal protection against influenza viruses, as recommended by the American Academy of Pediatrics and the Advisory Committee on Immunization Practices. 1, 2
Why Annual Vaccination is Necessary
Annual vaccination is essential for several reasons:
- Virus Mutation: Influenza viruses frequently change, with vaccine strains often updated annually based on global surveillance of circulating strains 1
- Waning Immunity: Studies demonstrate that post-vaccination antibody titers decline over the course of a year 1
- Optimal Protection: Annual vaccination provides the best protection against seasonal influenza, which typically circulates from October to May 1
Timing of Annual Vaccination
- Ideal timing: Vaccination should be administered as soon as it becomes available, preferably before the end of October 2
- Continued availability: Vaccination should continue to be offered throughout the entire influenza season, even after influenza activity has been documented in a community 1
- Extended protection: Since influenza season often extends into March and beyond, immunization through May 1 can still provide protection during that particular season 1
Special Considerations by Age Group
Children Under 9 Years
- First-time vaccination: Children receiving the vaccine for the first time require 2 doses separated by at least 4 weeks 2
- Second season: Children who received only 1 dose in their first year of vaccination should receive 2 doses the following season 1
- Subsequent seasons: After receiving appropriate initial dosing, only 1 dose per year is needed 1
Individuals 9 Years and Older
- Single dose: Only 1 dose of influenza vaccine is required annually 2
Vaccine Effectiveness
- Overall effectiveness: Vaccine effectiveness typically ranges from 40-60% when influenza vaccines are antigenically matched to circulating viruses 3
- Duration of protection: Studies show that vaccine effectiveness may decline over the course of the season, with protection waning by approximately 7% per month for influenza A(H3N2) and influenza B 1
- Continued benefit: Even with waning effectiveness, vaccination provides protection for at least 5-6 months after administration 1
Common Pitfalls to Avoid
- Delaying vaccination: Do not delay vaccination in hopes of extending protection later into the season, as this increases the risk of missing vaccination altogether 1
- Assuming lifetime immunity: Unlike some vaccines that provide long-term protection, influenza vaccination must be repeated annually due to virus mutation and waning immunity 1
- Stopping too early: Vaccination efforts should continue throughout the entire influenza season, as there may be more than one peak of activity during a season 1
Key Takeaways
- Influenza vaccination is recommended annually for all persons aged ≥6 months without contraindications
- The vaccine composition may change each year based on circulating strains
- Annual vaccination is necessary even when vaccine strains remain unchanged from the previous season
- Vaccination should ideally occur before the end of October but should continue to be offered throughout the influenza season