The vaccines for the coronavirus disease 2019 (Covid-19) from Pfizer-BioNTech and Moderna provide protection against the virus that may last for years, a study published Monday by the journal Nature found.

Both of the two-dose vaccines produce antibodies – cells made by the immune system to fight off viruses – that recognize the coronavirus and remain active for at least 15 weeks, the data showed.

After infection or vaccination, germinal centers form in the lymph nodes and create memory B cells that prime the immune system to recognize viruses over the long term.

The findings suggest that most people who received the vaccines may not need boosters, provided the virus and its variants do not mutate significantly, and that the vaccines offer long-term protection, the researchers said.

“We found that germinal centers were still going strong 15 weeks after the vaccine’s first dose,” study co-author Ali Ellebedy said in a press release.

The body’s immune response is formed in germinal centers, and the longer they last, “the stronger and more durable our immunity will be,” Ellebedy said.

“Germinal centers are the key to a persistent, protective immune response,” said Ellebedy, an associate professor of pathology and immunology at Washington University of St. Louis.

Those who have recovered from Covid-19 before being vaccinated may not need boosters, even if the virus undergoes more marked changes, though older adults and people with weakened immune systems might need boosters.

People who recover from Covid-19, these memory B cells remain in bone marrow for at least eight months after infection, based on findings published last month by Ellebedy and his colleagues, also by Nature.

These earlier findings indicated that immunity might last years in people sickened with the virus and later vaccinated, though it remained unclear whether vaccination alone would have a similar effect, the researchers said.

In this new study, all 14 participants still had active germinal centers against the coronavirus 15 weeks after receipt of their first dose of the vaccines.

In addition, participants’ levels of memory B cells had not declined in that time, despite the fact that germinal centers typically peak one to two weeks after vaccination, before declining, the researchers said.

The study did not evaluate the immune response offered by Johnson & Johnson vaccine, according to Ellebedy.

However, because it is a different type of vaccine, it is expected that the immune response would be less durable than those produced by the Pfizer-BioNTech and Moderna products, he said.

“We’re still monitoring the germinal centers, and they’re not declining — in some people, they’re still ongoing, [which] is truly remarkable,” Ellebedy said.

“There’s a fierce selection process happening there, and only the best immune cells survive,” he said.