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ST. LOUIS — A new study suggests the Pfizer and Moderna COVID-19 vaccines set off an immune response that is strong enough to last for years, WTVO reported.

The study, published Monday in Nature, found evidence that the vaccines induced a persistent immunity to COVID-19, and that those who received either vaccine may not need a booster shot.

That’s assuming that the coronavirus and its variants do not significantly evolve, according to the study, led by researchers at Washington University School of Medicine in St. Louis.

“Anything that would actually require a booster would be variant-based, not based on waning of immunity,” Dr. Deepta Bhattacharya, an immunologist at the University of Arizona, told The New York Times. “I just don’t see that happening.”

Both vaccines were developed using mRNA technology, which gives the body’s immune system instructions to identify and protect against foreign bodies such as the spike protein found in SARS-CoV-2, the virus that causes COVID-19.

Researchers found the immune cells created to fight the virus were present nearly four months after receiving the first dose of the vaccine.

“We found that germinal centers were still going strong 15 weeks after the vaccine’s first dose,” said senior study author Ali Ellebedy, PhD. “We’re still monitoring the germinal centers, and they’re not declining; in some people, they’re still ongoing. This is truly remarkable.”

According to the New York Times, scientists still don’t fully understand why some vaccines induce protection that lasts a lifetime while others, such as the smallpox vaccine, require booster shots.

“If you’ve already been infected and then you get vaccinated, you get a boost to your antibody levels,” said the study’s co-author, Dr. Jane O’Halloran. “The vaccine clearly adds benefit, even in the context of prior infection, which is why we recommend that people who have had COVID-19 get the vaccine.”