A new government-funded investigation this week should offer some comfort to people who have survived covid-19. It suggests that they have a low risk of coronavirus reinfection, at least about three months later.
Researchers from the National Cancer Institute partnered with commercial testing labs and two health data collection companies for this study. published Wednesday at JAMA Internal Medicine.
They analyzed unidentified data from more than 3 million Americans who had been tested for commercial antibodies to SARS-CoV-2, the coronavirus that causes covid-19, sometime between January and August 2020. antibodies, although not perfect, indicate if someone has had a previous previous infection. These people were divided between those who had antibodies and those who did not, according to the tests. The researchers then examined how many people in both groups subsequently obtained a PCR test of covid-19, which is intended to diagnose an active infection.
Approximately 10% of the people in each group went on to take a PCR test. There are more people with antibodies who tested positive for the virus during the first 30 days after the antibody test than those who did not have antibodies. But this is not surprising, as detectable traces of the virus can remain in the body for months, even after the symptoms have passed and the person is no longer infectious. Therefore, it is likely that these positive PCR results used to detect the first infection. When the researchers specifically examined the positive test rate after the first month and, most importantly, more than 90 days later, long enough for a positive PCR test to indicate true reinfection, the results were encouragingly different.
After three months or more, only 0.3% of people with a previous positive antibody test tested positive for coronavirus again, compared with 3% of people with a negative antibody test. In other words, having a past infection was associated with a much lower risk of infection three or more months later.
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“People who have recovered from covid-19 should be assured that being antibody-positive is associated with some protection against a new infection,” the author of the e-mail said in an email. study Douglas Lowy, deputy director general of the NCI.
Still, the findings come with their limitations. On the one hand, they cannot tell us exactly what protection a past infection will provide against reinfection or how long it is expected to last (although other research has suggested which can take years). Another factor that this study cannot take into account is the recent emergence of coronavirus variants. Some, like that first identified in South Africa, last year, they are believed to increase the risk of reinfection, as they may be able to partially evade the immune response created by a previous infection or vaccination.
However, there is no research to show that any variant that is currently being spread can completely elude natural immunity or the vaccine provided by someone. Our immune system has it many weapons against a known germ, and most reinfections are likely to be milder than the first time.
Even before these new variants existed, there were documented cases of reinfection, including cases where symptoms were worse on the second course. And the findings of the new study still suggest that reinfection occurs, though rarely. Therefore, no one should assume that it is impervious to covid-19 just because it survived a previous infection without any problems. Ultimately, the best way to protect everyone from covid-19 is to vaccinate as many people as possible, including those who have already had the viral disease., according to Lowy. It is a remedy that carries far fewer risks than suffering from a natural infection.
“People who have recovered from covid-19 should still plan to get vaccinated when given the opportunity,” he said.
The NCI plans to continue funding research that will track the prevalence of reinfection in the general public, along with studies that will examine how our immune response to the virus may change over time and against new variants.