How Effective is an Annual Flu Shot?

How Effective is an Annual Flu Shot?

Not sure if getting the flu shot every year is beneficial?

Past studies have suggested that annual vaccinations may lessen the shot’s effectiveness, though they’ve been inconsistent or inconclusive.

Now, a new and larger study has found that getting a flu shot every year can actually increase immunity in some cases.

The study, recently published in JAMA, found that children – using data from more than 3,000 kids ages 2 to 17 – who had been vaccinated during the current flu season, as well as the previous one, were no more likely to have been diagnosed with influenza than those who’d been vaccinated during the current season only.

The data included varied flu types, vaccine types, and by year. Overall, no combination of scenarios found vaccinations two years in a row were associated with lower effectiveness than flu shots in only the current season or year.


“In other words, there was no evidence of diminished vaccine effectiveness in frequent vaccines, even though the study included seasons in which such effects had been reported elsewhere,” wrote Sarah Cobey, PhD, associate professor of ecology and evolution at the University of Chicago, in a related commentary.

Since the study focused exclusively on children, there’s no evidence that the same patterns would apply to adults. But, a study published earlier this year in Canadian Medical Association Journal did find that repeated vaccination is protective for people over 65.

Related: Why You Need to Get Your Flu Shot

With dissimilar flu seasons, and vaccine’s having varying levels of potency every year, the study authors admit there’s more work to be done.

“To better understand the effect, if any, of repeat vaccination on vaccine effectiveness, additional studies are needed each season, for each vaccine type, in different populations,” Huong McLean, PhD, a research scientist at the Marshfield Clinic Health System and first author of the study, told

For children at least, it does seem to be beneficial to get that flu shot every year.

“Getting the flu shot every year is still the best way to protect against the flu,” McLean says.

Photo Credit: TaTAE Thailand/; CNK02/

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