If you’re fully vaccinated against COVID-19, you’ve probably breathed a sigh of relief. But how long can you expect that feeling to last? The CDC has yet to hazard a guess as to the durability of post-vaccine immunity on their website, but a few studies have given us some clues.
And so far, it’s mostly good news. A letter from a vaccine research group to the New England Journal of Medicine in April (you can think of these letters like mini studies) found that people still had strong protection six months after receiving their second dose of the Moderna vaccine. The group writes: “Although the antibody titers and assays that best correlate with vaccine efficacy are not currently known, antibodies that were elicited by mRNA-1273 persisted through 6 months after the second dose, as detected by three distinct serologic assays.” Pfizer also announced in April that it found people who had received the Pfizer vaccine still had strong protection six months after their second dose.
These study results don’t mean that protection only lasts six months, just that so far, at the six-month checkpoint, immunity is still going strong. Remember that both vaccines were authorized in December, so the vaccine has only been on the market for six months. Even vaccine trial subjects had an average of only two months of follow-up data at the time the vaccine makers applied for authorization, so they’re just a little bit ahead of the rest of us. (The Johnson & Johnson vaccine is running on a later schedule than the rest, since its trials finished a few months after the other two.)
Trials with booster shots have already begun, but so far it looks likely that it will be at least a year before anybody needs one, and possibly longer. Immunity is a complex thing, and scientists still haven’t nailed down a test that can tell the difference between someone who is protected against COVID-19 versus someone who is still susceptible. We’ll most likely learn more in the coming months, but for now, we can probably be secure in the knowledge our vaccines are good for at least six months, probably at least a year, and maybe longer.