COVID-19 survivors have an approximately tenfold increase in protection against the virus, according to a government-funded study published Wednesday.
Why it matters: There have been a few documented cases of reinfection that have caused survivors to be concerned about no immunity. Although there are still questions about how much or how long immunity lasts and what the impact of variants is, this vast set of observational data is proof that protection exists.
The latest: The study, published in JAMA Internal Medicine, commercial SARS-CoV-2 antibody test data from 3.2 million U.S. patients examined from January 1 and August 23, 2020.
- Of those who initially tested antibody-negative and later tested for active infection, they found that 3% were positive for SARS-CoV-2 for 90 days or more.
- Of those who were initially antibody-positive and later tested for active infection, they found that only 0.3% were 90 days or more positive for SARS-CoV-2.
- “There’s a tenfold decrease, which is essentially a 90% reduction in the risk for people who are antibody positive,” said Doug Lowy, co-author and deputy director of the National Cancer Institute, who conducted the study.
- “This is something that has been assumed for a long time, but our study is by far the largest study being looked at, especially in the United States,” says Lowy.
Warning: Because the study examined real-time data and was not done in a clinical trial, there could be ‘confusions’ or distorting factors influencing the results, Lowy says. That means the tenfold protection is a rough average – in fact, “maybe it’s a threefold difference, and maybe it’s a twentyfold difference.”
- However, the results are consistent with another recent report NEJM study from the UK that also found an approximately tenfold difference, he says.
What they say: Jennifer Juno, a senior research fellow at the University of Melbourne’s Doherty Institute, who was not part of the study, says “several studies now suggest that previous infections do indeed provide protection against re-infection, as we would expect.”
- “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-authored another paper published last week in Nature communication look at the level of antibodies in humans during a period of four months after infection. They found:
- Humans tend to initially have strong neutralizing antibodies that decrease rapidly by about 50% within 55 days, but which decrease and decrease plateaus.
- And then other immune system actors take over. Juno says the level of B cells that produce antibodies to the coronavirus protein has increased over time in their study participants.
- “This is encouraging news because it suggests that the immune system is generating a strong memory response to infection, which is likely to play a role in protecting re-infection,” she adds.
The whole picture: Vaccination is still highly recommended for those who have been infected before, Lowy and Juno say.
- “Early studies suggest that individuals who were previously infected significantly increased their antibody levels after receiving one dose of COVID vaccine, which indicates a great benefit of receiving the vaccine, even if you have been infected before,” says Juno. .
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