If you are fully vaccinated, you may be excited about gathering with family and friends again. You might even be planning a winter vacation. But there are still nagging questions about how long protection from the coronavirus vaccines will last. For instance, will your shot wear off gradually or suddenly? Will you need a booster? Unfortunately, we can’t answer these questions with certainty yet. While the vaccines have provided strong protection against COVID-19 up to now, scientists need to monitor them over a longer period to fully understand their capabilities.
“We can only say that a vaccine is protective as long as we are measuring it,” says Yale Medicine infectious diseases specialist Jaimie Meyer, MD, MS.
In the meantime, there are a few things we know. One is that the Pfizer-BioNTech and Moderna mRNA vaccines have performed well so far. The most recent Pfizer-BioNTech data shows 91% overall efficacy falling to 84% at the six-month mark, and a steady 97% against severe disease, based on a July preprint that has not been reviewed by outside scientists. Moderna’s vaccine was 93% effective overall through six months and 98% effective against severe disease, according to a company statement in August. The latest data does not specify effectiveness against Delta.