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COVID-19 survivors tend to have about tenfold protection against the virus, according to a government-funded study released Wednesday.
Why is this important: There have been a few documented cases of reinfection leading to concern that survivors will not get any immunity. While questions remain about the length or duration of immunity and the impact of variants, this large observational body of data strengthens the evidence that there is some protection.
The last: The study, published in JAMA Internal Medicine, examined data from commercial anti-SARS-CoV-2 antibody tests of 3.2 million U.S. patients between Jan.1 and Aug.23, 2020.
- Of those who initially tested negative for antibodies and then were tested for active infection, they found 3% were positive for SARS-CoV-2 90 days or later.
- Of those who were initially positive for antibodies and then tested for active infection, they found that only 0.3% were positive for SARS-CoV-2 90 days or later.
- “There is a tenfold decrease, which is basically a 90% reduction in risk for people who are positive for antibodies,” says Doug Lowy, co-author and deputy director of the National Cancer Institute, which conducted the study.
- “It’s something that has been issued for a long time, but our study is by far the largest study looking at this, especially in the United States,” Lowy says.
Caveat: Since the study examines data in real time and was not performed in a clinical trial, there could be “confounding factors” or distorting factors that affect the results, Lowy points out . This means that the tenfold protection is a rough average – in reality, “maybe it’s a triple difference, and maybe a twenty times the difference.”
- However, the results correspond closely to another recent NEJM study from the UK which also found a difference roughly ten times as high, he says.
What they say: Jennifer Juno, a senior researcher at the University of Melbourne’s Doherty Institute who was not part of the study, says that “several studies now suggest that the previous infection does provide protection against re-infection, as could be seen. ‘wait there. “
- “The key questions we need to address now include understanding the duration of this protection and the specific immune responses that are most strongly associated with protection,” she says.
Juno co-wrote a different article published last week in Nature communications by looking at the level of antibodies in people over a period of four months after infection. They found:
- People tend to have strong neutralizing antibodies initially which decrease rapidly by about 50% in 55 days, but slow down and slow down.
- And then other players in the immune system resume. The level of B cells that produce antibodies to the coronavirus spike protein increased over time in study participants, rather than decline, Juno says.
- “This is encouraging news, as it suggests that the immune system generates a robust memory response to infection, which is likely to play a role in providing some protection against reinfection,” she adds.
The big picture: Vaccination is still strongly recommended for those who have been infected previously, say Lowy and Juno.
- “Early studies suggest that people who were previously infected show a substantial increase in their antibody levels after receiving a dose of a COVID vaccine, indicating a great benefit from receiving the vaccine even if you have already been infected. Juno says.
Go further: Obstacles we face before achieving collective immunity
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