New evidence that Covid-19 antibodies reduce the risk of reinfection


A healthcare worker takes a drop of blood for a Covid-19 antibody test at the Diagnostic and Wellness Center in Torrance, California, on May 5, 2020. Valerie Macon / AFP / Getty Images

Covid-19 antibodies from a previous infection could significantly reduce the risk of re-infection, according to a study published Wednesday in the journal JAMA Internal Medicine.

“The study results are basically a 10-fold reduction, but I’d have some caveats about it. In other words, it could be an overestimate of the reduction, it could be an underestimate of the reduction,” said Dr. Douglas Lowy. , senior deputy director of the National Cancer Institute, who was one of the study’s authors.

“For me, the big message is: there is a reduction,” he said. “The main conclusion is that having positive antibodies after a natural infection is associated with partial protection against a new infection.”

How they did the study: The researchers examined data from more than 3.2 million people in the United States who had completed an antibody test in the past year between January and August.

Among those tested, 11.6% tested positive for Covid-19 antibodies and 88.3% tested negative.

  • 0.3% of those with antibodies tested positive for Covid-19 infection later, beyond 90 days.
  • 3% of those who did not have antibodies tested positive for reinfection during the same time period.

But more research is needed to determine a causal relationship, how long protection against antibodies can last, and the risk of reinfection from a variant.

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