According to a government-funded study published Wednesday, COVID-19 survivors tend to increase about one-tenth of virus protection.
Why it’s important: There are some documented cases of reinfection that have caused survivors to worry about not getting any immunity. Although questions remain about how long or how long immunity lasts and what the impact of the variants will be, this large set of observational data reinforces the evidence that there is some protection.
The last: The study, published in JAMA Internal Medicine, examined commercial SARS-CoV-2 antibody test data from 3.2 million U.S. patients from January 1 to August 23, 2020.
- Of those who had initially tested negative antibodies and subsequently tested for active infection, they found that 3% were positive for SARS-CoV-2 90 or more days later.
- Of those who were initially positive and later tested for active infection, they found that only 0.3% were positive for SARS-CoV-2 90 or more days later.
- “There’s a tenfold decrease, which is essentially a 90% reduction in risk for people who have positive antibodies,” says Doug Lowy, co-author and deputy director of the National Cancer Institute, which conducted the ‘study.
- “It’s something that has been hypothesized for a long time, but our study is by far the largest study that has been analyzed, especially in the United States,” Lowy says.
Warning: Because the study examines the data in real time and was not done in a clinical trial, there may be “confounding factors” or distorting factors that affect the results, Lowy points out. This means that protection for ten is an approximate average: in reality, “maybe it’s a triple difference and maybe it’s a twenty-fold difference.”
- However, the results closely match a recent one NEJM a UK study that also found a difference about ten times, he says.
What they say: Jennifer Juno, a senior researcher at Doherty Institute at the University of Melbourne who was not part of the study, says “there are now several studies suggesting that previous infection provides protection against reinfection, 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,” he says.
Juno co-authored a different paper published last week in Communications on Nature observing the level of antibodies in people over a period of four months after infection. They found:
- People usually have strong neutralizing antibodies initially that decrease rapidly by about 50% in 55 days, but that decrease altitudes and plateaus.
- And then other actors in the immune system recover. The level of antibody-producing B cells against the coronavirus peak protein increased over time in study participants, rather than decreasing it, Juno says.
- “This is encouraging news, as it suggests that the immune system generates a solid memory response to infection, which will likely play a role in protection against reinfection,” he adds.
The big picture: According to Lowy and Juno, vaccination is still highly recommended for those who have been infected before.
- “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, which points to a great benefit from receiving the vaccine even if you have been previously infected, ”says Juno.
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