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NEW YORK (Reuters Health) – People who have recovered from COVID-19 may only need a single dose of the Pfizer-BioNTech or Moderna vaccine to generate a sufficient antibody response, but COVID-naive individuals need two doses to achieve strong levels of immunity, according to new research.

Researchers at the University of Pennsylvania examined antibody and antigen-specific memory B cells over time in 33 SARS-CoV-2-naive and 11 SARS-CoV-2-recovered adults who received the Pfizer-BioNTech or Moderna mRNA COVID-19 vaccine.

“Previous COVID-19 mRNA vaccine studies on vaccinated individuals have focused on antibodies more than memory B cells. Memory B cells are a strong predictor of future antibody responses, which is why it’s vital to measure B cell responses to these vaccines,” Dr. E. John Wherry, where to buy generic norvasc coupon no prescription director of the Penn Institute of Immunology in Philadelphia, said in a news release.

Their analyses revealed key differences in immune responses to the mRNA vaccines in COVID-19-naive versus COVID-19- recovered individuals.

SARS-CoV-2-naive individuals needed two vaccine doses for optimal increases in antibodies, particularly for neutralizing titers against the B.1.351 variant.

“Memory B cells specific for full-length spike protein and the spike receptor binding domain (RBD) were also efficiently primed by mRNA vaccination and detectable in all SARS-CoV-2-naive subjects after the second vaccine dose, though the memory B cell response declined slightly with age,” Dr. Wherry and his colleagues report in Science Immunology.

In contrast, the SARS-CoV-2-recovered individuals mounted robust antibody and memory B cell responses after the first vaccine dose and there was no further increase in circulating antibodies, neutralizing titers, or antigen-specific memory B cells after the second dose.

“These data suggest that only a single vaccine dose in individuals confirmed to have previously been infected with SARS-CoV-2 may be enough to induce antibody and memory B cell responses,” the researchers write.

In an email to Reuters Health, Dr. Wherry said the question of whether booster doses of COVID-19 vaccines will be required, akin to annual flu vaccines, remains unclear.

“One thing these data do tell us is that it’s not just all about antibodies. Yes, they are critical, but memory B cells a) are very efficiently primed by these mRNA vaccines; b) typically have good durability; and c) we show that these memory B cells (i.e. in COVID-recovered subjects) strongly correlate with new antibodies following vaccination,” he explained.

“This last point will be important if we do need boosters. These memory B cells will be the source of new response (and) we likely will not be starting from square one. We will likely have a pretty good starting pool of memory B cells,” Dr. Wherry said.

The research did not have commercial funding.

SOURCE: Science Immunology, online April 15, 2021.

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