Story at a glance

  • Experts are still learning about immune responses to the novel coronavirus and the vaccines.
  • A small study finds evidence that suggests that people who have recovered benefit from one dose of Pfizer/BioNTech or Moderna vaccines but may not receive additional benefit from a second dose.
  • The researchers are conducting large scale studies to further investigate this.

A team of researchers at the Penn Institute of Immunology took blood samples from 44 study participants before and while they were receiving either the Pfizer/BioNTech or Moderna vaccines. Of the participants, 33 were naive to the SARS-CoV-2 coronavirus and 11 were recovered from previous SARS-CoV-2 infection.

The researchers took blood samples four times: baseline, 2 weeks post-primary immunization, day of booster immunization, and 1 week post-booster immunization, according to the paper published in Science Immunology. In their analysis, they focused on looking for memory B cells, which are important for long-term immunity. “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," says E. John Wherry in a press release. "This effort to examine memory B cells is important for understanding long-term protection and the ability to respond to variants."


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They also tested for antibodies, which for recovered participants they did not see an increase after the second vaccine dose. SARS-CoV-2 antigen-specific B cells were minimal in naive individuals but were present in recovered people. The researchers also saw that B cells were significantly boosted in naive people after the second vaccine dose while recovered people had a “robust expansion” after the first dose. They write in the paper, “a single dose of mRNA vaccine amplified pre-existing antigen-specific memory B cells in SARS-CoV-2 recovered subjects, with no additional quantitative benefit after the second vaccine dose.”

However, these results are for a very small sample size of only 11 people who recovered from the coronavirus. The researchers are continuing with larger scale studies to examine further if COVID-19 recovered individuals should get a one or two dose regimen and to see how long the antibodies last, according to the press release.


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Published on Apr 29, 2021