How Long Does Flu Shot Protection Last?

Influenza usually begins in early fall and peaks between December and February, so getting a flu vaccine before the month of November is suggested to protect against severe disease and death. On average, flu shots provide protection for 6 to 8 months, although an individual’s immune system is likely to affect the durability of a vaccine, according to Judith James, MD, PhD, vice president of clinical affairs at the Oklahoma Medical Research Foundation.

The influenza virus mutates rapidly, so the flu vaccine must be different every year. Consequently, experts recommend getting a new flu vaccine annually.

For children aged 6 months to 8 years who are getting their first flu shots, the CDC recommends 2 doses that are spaced out at least 4 weeks. Children in this age group are more likely to benefit from boosters, because their bodies must develop a protective response against the influenza virus. Two doses of the vaccine were also shown to decrease their risk of contracting influenza by approximately 50%.

For adults, 2 doses of the flu vaccine have not been shown to have more benefits than 1 dose, so adults are advised to only get 1 dose each influenza season.