At least 200 million people worldwide have struggled with long COVID: a slew of symptoms that can persist for months or even years after an infection with SARS-CoV-2, the virus that causes COVID. But research suggests that that number would likely be much higher if not for vaccines.

A growing consensus is emerging that receiving multiple doses of the COVID vaccine before an initial infection can dramatically reduce the risk of long-term symptoms. Although the studies disagree on the exact amount of protection, they show a clear trend: the more shots in your arm before your first bout with COVID, the less likely you are to get long COVID. One meta-analysis of 24 studies published in October, for example, found that people who’d had three doses of the COVID vaccine were 68.7 percent less likely to develop long COVID compared with those who were unvaccinated. “This is really impressive,” says Alexandre Marra, a medical researcher at the Albert Einstein Israelite Hospital in Brazil and the lead author of the study. “Booster doses make a difference in long COVID.”