When should an individual receive the influenza (flu) vaccine?

From the Guidelines

The best time to get the flu vaccine is in early fall, ideally by the end of October, before flu season begins in earnest. This recommendation is based on the most recent and highest quality study, which suggests that children 6 months through 8 years of age who are receiving an influenza vaccine for the first time or who have received only 1 dose before July 1,2019, should receive 2 doses of influenza vaccine ideally by the end of October 1.

Key Considerations

• The flu vaccine takes about two weeks to become fully effective as your body builds immunity, so earlier vaccination provides better protection.
• Annual vaccination is necessary because flu viruses constantly change, and vaccine protection decreases over time.
• Everyone 6 months and older should get vaccinated each year, with special emphasis on high-risk groups like young children, pregnant women, adults over 65, and those with chronic health conditions.
• The standard flu vaccine is typically given as a single dose injection, though some people (particularly children ages 6 months to 8 years who have never been vaccinated) may need two doses spaced four weeks apart.

Prioritization

• High-risk groups, such as young children, pregnant women, adults over 65, and those with chronic health conditions, should be prioritized for vaccination.
• Household contacts of persons at high risk, including out-of-home caregivers and household contacts of children aged 0--23 months, should also be prioritized for vaccination 1.

Additional Considerations

• Vaccination efforts should focus on persons at high risk and health-care workers in October and earlier, with vaccination of all other groups beginning in November 1.
• Materials to assist providers in prioritizing early vaccination are available at http://www.cdc.gov/flu/professionals/vaccination/index.htm.

From the Research

Influenza Vaccine Timing

The influenza vaccine is recommended for all individuals 6 months of age or older, including pregnant and postpartum women, unless there is a contraindication 2, 3, 4.

• The vaccine should be administered at the beginning of the flu season, which typically starts in October 2.
• It takes approximately 14 days after vaccination for a healthy adult to reach peak antibody protection 2.
• Vaccination soon after the vaccine becomes available can be considered for pregnant women in the third trimester 3.
• Children who need 2 doses should receive their first dose as soon as possible after the vaccine becomes available to allow the second dose to be received by the end of October 3.
• For nonpregnant adults, vaccination in July and August should be avoided unless there is concern that later vaccination might not be possible 3.

Considerations for Vaccine Effectiveness

• The effectiveness of the influenza vaccine may wane during the course of a single season, with the odds of testing positive for influenza increasing by approximately 16% for each additional 28 days since vaccination 5.
• Interim estimates of seasonal influenza vaccine effectiveness have shown that the vaccine can still prevent illness, hospitalization, and death associated with currently circulating influenza viruses, even when the effectiveness may be lower than expected 6.
• The vaccine has been shown to provide substantial protection among children and adolescents aged 6 months-17 years, with an estimated vaccine effectiveness of 55% 6.

Special Considerations

• Influenza vaccination is especially important during the COVID-19 pandemic, as it can help reduce symptoms that might be confused with those of COVID-19 and alleviate stress on the healthcare system 3, 4.
• Guidance for vaccine planning during the pandemic is available, and healthcare providers should check the CDC's influenza website periodically for updates and additional information 3, 4.