COVID-19 immunity persists for at least a year, perhaps even a lifetime, according to two recent studies, The New York Times reported May 26.
The first study, published in Nature May 24, involved 77 people who were infected with COVID-19 about a year earlier and had since recovered. Researchers focused on memory B cells, which retain a memory of the virus, and found that while the antibody levels in the participants' blood samples dropped in the months after infection, memory B cells lingered in the bone marrow, ready to produce antibodies as needed.
Among the 19 participants researchers were able to obtain bone marrow samples from, 15 had detectable memory B cells about seven months after infection, while four did not. This reinforces the added protection vaccines provide to those who've previously recovered from COVID-19, researchers said.
The second study, published in the pre-print server bioRxiv, included 63 people who also recovered from the coronavirus about a year earlier. Most participants had mild infections, and 26 had received at least one dose of mRNA vaccine. The findings showed that memory B cells evolved and strengthened overtime, with the antibodies they produced able to neutralize some of the virus variants. Further, the neutralizing ability was greatest among those who had received their shot.
Findings from the two studies suggest those who've been vaccinated on top of having recovered from a prior infection will never need a booster shot, while those who've been immunized and have never had COVID-19 will likely need boosters in the future.
"People who were infected and get vaccinated really have a terrific response, a terrific set of antibodies, because they continue to evolve their antibodies," explained Michel Nussenzweig, MD, PhD, lead author of the bioRxiv study and immunologist at New York City-based Rockefeller University. "I expect that they will last for a long time," he told the Times.