Two new studies show that immunity to the coronavirus may last for years and grows stronger after vaccinations, The New York Times reports. The key findings of the studies suggest that people who have contracted the virus and have been vaccinated will likely not need a booster shot. However, those who have received their jabs but have never tested positive for the virus may still need a booster. Both studies examined people who had been infected with the coronavirus about a year ago, and one of the studies found that certain cells will store the genetic information of the virus in bone marrow until it is needed to fight against infection. The other study, which is still under review, suggests that the aforementioned memory B cells grow stronger for at least another 12 months after initial infection.

“The papers are consistent with the growing body of literature that suggests that immunity elicited by infection and vaccination for SARS-CoV-2 appears to be long-lived,” said Scott Hensley, a University of Pennsylvania researcher who was not involved in the studies. Additionally, Michel Nussenzweig, a researcher who oversaw the study on cell maturation, told the Times that a vaccinated person who has previously been infected with the virus may not need a booster shot for variants, because they “will continue to evolve their antibodies.”