A new study aims to address when the best time is to get the flu shot.

An analysis from the University of Pittsburgh School of Medicine found that tens of thousands of flu cases and hundreds of deaths might be avoided if older adults wait until October to get the vaccine instead of when it first comes out in August. The results were published in the April issue of the American Journal of Preventive Medicine.

However, the authors noted there might be consequences to getting vaccinated later if the season arrives earlier than usual or people decide to skip the shot.

A previous study from 2017 found that protection from the vaccine wanes as the season progresses. Those who wait until it is closer to the start of flu season have greater immunity. But if only one in every 20 people who normally get the shot choose to skip it, all the gains would be negated, the study found.