Both the Pfizer-BioNTech and Moderna vaccines may provide lifetime protection against COVID-19, a new study suggests.
Researchers found that people who received either of the two-dose shots, which use new messenger RNA (mRNA) technology, had strong and 'persistent' immune responses.
What's more, the vaccines produced high levels of neutralizing antibodies against two variants of the virus.
This could mean that Pfizer and Moderna recipients could have long-lasting immunity - for years or potentially the rest of their lives - and may not even need boosters, reported first by The New York Times.
'It's a good sign for how durable our immunity is from this vaccine,' lead author Dr Ali Ellebedy, an immunologist at Washington University in St Louis told the newspaper
For the study, published on Monday in the journal Nature, the team recruited 14 people who received both doses of the Pfizer vaccine.
Among them, eight people had previously has been infected with COVID-19.
Researchers looked at lymph nodes, which produce a type of immune system cell known as a memory B cell.
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Memory B cells lock onto the surface of invading pathogens and mark them for destruction by other immune cells.
They also can circulate in the bloodstream for years - even decades - and the immune system can call up on them if there is another infection.
After someone is infected with COVID-19 or vaccinated against it, a germinal center forms in the lymph nodes, which acts a sort of 'boot camp' for memory B cells, according to The Times.
This center helps trains B cells to recognize the genetic sequence of the virus as well as any variants in this sequence.
The team took samples from the lymph nodes five times - at three weeks, four weeks, five weeks, seven weeks and 15 weeks after the first dose.
Results showed that even four months, the recipients had highly active germinal centers and the number of memory B cells that recognized the virus had not fallen.
Ellebedy told The Times that with most vaccine , germinal centers peak at one or two weeks post-immunization before fading.
'The fact that the reactions continued for almost four months after vaccination - that's a very, very good sign,' he said.
The stud survy found that participants also developed high levels of neutralizing antibodies against two variants: the Alpha variant, which originated in Kent, and the Beta variant, which originated in South Africa.
Researchers did not examine the vaccine's effect against the Delta variant, which was first identified in India, and is more transmissible than previous variants.
Although the study only looked at people vaccinated with Pfizer, Ellebedy said the findings can apply to Moderna because both vaccines used the same technology.
The study did not look at the coronavirus vaccine produced by Johnson & Johnson, but Ellebedy told The Times he does not think the immune response would be as strong because it uses different technology.
If booster shots are needed for J&J recipients, the extra dose could produce the same effect seen in COVID-19 survivors who were later immunized, meaning high levels of antibodies.
'If you give [memory B cells] another chance to engage, they will have a massive response,' Ellebedy told The Times.
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