Researchers in the United States have conducted a study showing the difference in antibody evolution following vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) between people who have not previously been infected with the virus and those who have.

The SARS-CoV-2 virus is the agent responsible for the ongoing coronavirus disease 2019 (COVID-19) pandemic that has now claimed the lives of more than 4.2 million people globally.

The team – from The Rockefeller University in New York – found that between a first (prime) and second (booster) shot of either the Pfizer-BioNTech or Moderna vaccine, the memory B cells of infection-naïve individuals produced antibodies that evolved increased neutralizing activity against SARS-CoV-2.

However, no additional increase in the potency or breadth of this activity was observed thereafter.

“Memory antibodies selected over time by natural infection have greater potency and breadth than antibodies elicited by vaccination,” says Michel Nussenzweig and colleagues.

The researchers say the findings suggest that boosting vaccinated individuals would elicit a quantitative increase in neutralizing activity, but not the qualitative advantage against SARS-CoV-2 variants produced when convalescent individuals are vaccinated.

A pre-print version of the research paper is available on the bioRxiv* server, while the article undergoes peer review.

B- cell responses evolve for at least a year in convalescent individuals

Following SARS-CoV-2 infection, B-cell responses continue to evolve for at least one year, with memory B cells expressing increasingly broad and potent antibodies that are resistant to the mutations found in variants of concern.

Vaccinating convalescent individuals, therefore, elicits high levels of plasma neutralizing activity against such variants.

Now, Nussenzweig and colleagues have investigated the evolution of memory B cells following vaccination with either the Pfizer-BioNTech or Moderna’s vaccine in a cohort of 32 infection-naïve  (median age 34.5 years) who were recruited between January 21st and June 23rd, 2021.

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