Antibodies to the coronavirus decline over time, but the immune system has a back-up plan that doesn’t rely on boosters, according to a study by scientists at the University of Pennsylvania, where mRNA vaccine technology has been developed.
Researchers at the university’s Perelman School of Medicine followed 61 people for six months after vaccination with mRNA vaccines. The team noted that the antibodies gradually decreased, but the injections generated long-lasting immune memory against SARS-CoV-2 in the form of B and T cells that increased over time to help prevent serious illness.
“It was perhaps a little surprising,” said John Wherry, director of the Institute of Immunology, who works in the same faculty as mRNA pioneer Drew Weissman. The research was published on August 23 ahead of peer review and publication.
Fears that COVID vaccines would provide a weaker shield against the more transmissible delta strain in countries that started vaccinations early has prompted health officials to consider offering third doses to boost antibody levels. President Joe Biden said on Friday his administration plans to start offering additional injections as early as five months after receiving a second dose.
Although the third doses promise to strengthen antibodies and better block SARS-CoV-2 for longer, the body has its own natural support to defend against COVID-19 even when circulating antibody levels decline, a Wherry said.
“If the antibodies go down and you get a little local infection, you have memory B cells to renew themselves or react very quickly to make new neutralizing antibodies,” he said.
Antibodies on the mucous surfaces lining the nose and throat block the coronavirus at its front door, preventing it from causing infection. But, as the protective antibodies wear off, an infection is more likely to set in – at least until new antibodies are raised in response.
Wherry’s group found that memory B cells generated by mRNA vaccines made by Moderna Inc. and Pfizer Inc. and its partner BioNTech SE appeared to block viral variants, including alpha, beta, and delta better than those produced in response. to a mild case of COVID -19.
In addition, high levels of vaccine-induced T lymphocytes, a type of white blood cell capable of finding and killing cells infected with the virus, were detected after six months, “now an extra armor to protect us,” he said. Wherry said.
The findings help explain why vaccination remains effective in protecting against severe COVID-19, hospitalization and death even as more emerging infections occur.
“We see a drop in efficiency when you only measure whether people are infected, but really very stable immunity if you measure the results of serious illnesses,” Wherry said. “This fits with the idea that circulating antibodies will protect you from infection, but memory B cells and memory T cells, although they may not eliminate the ability to have a virus. in the nose, they will actually prevent serious disease. “
Immune safeguards will also shorten the duration of COVID symptoms, prevent them from getting worse and reduce the likelihood of transmitting SARS-CoV-2 infection to other people, he said.
“Vaccinated people are really not fueling this fire; it’s really unvaccinated people who are, ”said Wherry. “So that’s one more reason to get vaccinated.”
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