To stay protected against COVID-19, people may need booster shots within 12 months of receiving their initial vaccinations, David Kessler, the chief science officer for President Joe Biden’s COVID-19 response task force, said at a congressional committee meeting on Thursday (April 15), Reuters reports. Pfizer CEO Albert Bourla agrees with that timeline, according to comments he made to CNBC earlier this month.

So far, the evidence suggests that Pfizer/BioNTech’s and Moderna’s COVID-19 vaccines will protect against SARS-CoV-2 infection for at least six months. Beyond that, the data simply aren’t available yet.

“Unfortunately, many people have misunderstood that to mean that it lasts only six months, [when] all that information means is that we know that it lasts six months, and we expect it to last longer,” allergist and clinical immunologist Susan Bailey, the president of the American Medical Association, tells National Geographic.

Pfizer and BioNTech are now testing the efficacy of adding a third dose to their two-shot regimen, and Moderna announced this week that it was also working on a booster, which it hopes to have ready by the fall, according to CNBC. Meanwhile, Johnson & Johnson is testing the effects of adding a second jab to its one-and-done protocol. All of these companies are also working to develop updated formulations to target emerging SARS-CoV-2 variants.

“It’s highly likely” that booster shots or new vaccines will be “required in the future,” the University of Maryland School of Medicine’s Matthew Frieman, who is involved in the development of Novavax’s COVID-19 vaccine candidate, tells National Geographic. “How frequently we need them—and if they’re needed worldwide or in specific populations—is what we don’t know.”

See “SARS-CoV-2 Isn’t Going Away, Experts Predict