More data show COVID-19 boosters are effective against variants
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Researchers evaluated the immune responses of a few dozen people who received three doses of a COVID-19 messenger RNA vaccine and found, as other have, that a booster shot can protect people infected with a variant from becoming very ill.
Frauke Muecksch, PhD, a postdoctoral researcher at The Rockefeller University in New York, presented findings from the study this week at the Conference on Retroviruses and Opportunistic Infections, a day after they were published online by the preprint server bioRxiv.
Muecksch and colleagues evaluated antibody and memory B cell responses elicited by a booster vaccination among 43 SARS-CoV-2-naive study participants who were recruited between Jan. 21 and Dec. 14, 2021.
They tested participants at four separate time points — once after receiving their first vaccine dose, 1 month and 5 months after receiving a second dose, and 1 month after receiving a third booster dose. Participants were aged between 23 and 78 years, with a median age of 34 years. More than half (23) were women.
“Antibodies elicited after the booster dose are indeed significantly more potent than those that were isolated after the second vaccine dose,” Muecksch said during her presentation. “The potency of these antibodies is very comparable to those that we can find in convalescent individuals roughly 1 year after infection.”
She said a booster dose “is able to boost plasma neutralizing antibody titers against viral variants, such as the beta, the delta and the omicron variants.”
“In fact,” she said, “in the case of the omicron variant, the booster dose leads to an almost 40-fold increase in neutralizing titers.”
According to Muecksch and colleagues, boosting not only increased plasma neutralizing activity but also increased the number of receptor binding domain-specific memory B cells.
“The monoclonal antibodies generated by those cells have greater somatic hypermutation and increased neutralizing activity when compared to antibodies generated after the second dose, indicative of continued evolution of the humoral response to SARS-CoV-2,” they explained. “A substantial fraction of the monoclonal antibodies isolated after the third dose of an mRNA vaccine are able to neutralize pseudoviruses representing the delta and omicron variants, at low antibody concentrations.”
“This antibody evolution and the consequent production of proxy active neutralizing antibodies, taken together with the increase in antigen specific memory B cells, provides the explanation why currently available mRNA vaccines are so effective in protecting us from severe disease, even after infection with circulating variants,” Muecksch said.
References:
Muecksch F, et al. bioRxiv. 2022;doi:10.1101/2022.02.14.480394.
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Muecksch F, et al. Abstract 125. Presented at: Conference on Retroviruses and Opportunistic Infections; Feb. 12-16, 2022 (virtual meeting).
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