This Is the Best Time to Get a Flu Shot

Getting the flu shot any time during respiratory virus season is better than not getting it at all. But vaccine protection wanes, so timing the shot properly can help antibodies peak when cases are highest.

Researchers wanted to figure out the optimal time for getting a flu shot, and took advantage of the fact that children tend to get vaccinated in the month they were born. In a study published in BMJ, they analyzed Health insurance data from more than 800,000 children, ages 2-5, who got a flu shot from 2011 to 2018. The data showed that kids vaccinated in October had the strongest protection—they were about 12% less likely to get the flu compared to kids vaccinated in August.

“It makes sense that October is the ideal time to get vaccinated,” says the study's senior author Dr. Anupam Jena, professor of Health care policy at Harvard Medical School and professor of medicine at Massachusetts General Hospital. Get vaccinated in August or September, and immunity might wane too soon; get the shot in December or January, and immunity might not have time to build up before the December or January peak, he says. October seems to be the sweet spot. "These findings provide a data-driven way to show that’s true.”

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Pediatricians could put this finding into practice by discussing optimal timing of the shot and “doubling down on October appointments,” says Jena. “To the extent that they can more forcibly advocate that October is the optimal time for kids to get vaccinated, we might see parents moving to get shots in that month.”

Other strategies may include focusing on school-based vaccination programs. “For things like flu vaccines, convenience is a really big deal, and making them more available in school would solve the problem of many kids not getting vaccinated in the first place, as well as facilitating optimal timing,” says Jena.

Getting the flu shot in October could also be important in helping children with weakened immune systems get the best protection possible against severe illness and hospitalization. “If you are at risk of having flu-related complications, optimal timing of the shot may matter even more,” says Jena. “For those kids, they get a larger bang for their buck if they are vaccinated in October.”

Since the study only involved children, it’s not clear if the same effect will hold for adults. But since children are among the most efficient spreaders of the flu, making sure kids are protected could also lead to fewer cases among adults, Jena says. “If kids are going to get vaccinated, you might as well optimize the time at which they get the shot."