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Covid-19 survivors have low risk of reinfection



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photo: Simon Dawson (Getty Images)

The new government-funded research this week should provide some comfort to those who survived covid-19. This shows that after at least three months, they have a lower risk of reinfection with the coronavirus.

Researchers from the National Cancer Institute collaborated with commercial testing laboratories and two medical data collection companies to conduct this research. Published On Wednesday in JAMA Internal Medicine.

They analyzed de-identified data from more than 3 million Americans who have been tested for commercial antibodies against SARS-CoV-2, a coronavirus that causes covid-19, from January 2020 to 2020 August. Someone has been infected recently. According to the test, these people are divided into those with antibodies and those without antibodies. The researchers then looked at how many of the two groups later received a PCR test for covid-19, which is designed to diagnose active infections.

About 10% of people in each group continued to undergo PCR testing. Among those without antibodies, those with antibodies will have a positive reaction to the virus within the first 30 days after the antibody test. But this is not surprising, because even after the symptoms disappear and the person is no longer infectious, detectable traces of the virus will remain in the body for several months. Therefore, these positive PCR results are usually the first infection. When researchers performed a positive test after the first month, especially within 90 days (especially after 90 days), the positive reaction rate was high (enough time may indicate a real re-infection), and the results are encouraging.

After three months or more, only 0.3% of people who tested positive for the earlier antibody tested positive for the coronavirus again, while only 3% of people who tested negative for the antibody. In other words, past infections are related to a greatly reduced risk of infection after three months or more.

Douglas Lowy, NCI’s chief deputy director, said in an email: “People who have recovered from covid-19 should be assured that positive antibodies are related to some prevention of new infections.”

However, this discovery does have its limitations.First, they can’t tell us how much past infections will provide protection against reinfection, or how long they are expected to last (although other studies have suggested It may take several years). Another factor that this study cannot explain is the recent emergence of coronavirus variants.Some-like one First determine The disease in South Africa last year was believed to increase the risk of re-infection because they may be able to partially escape the immune response from early infection or vaccination.

However, there is no research showing that any currently circulating variants can completely evade someone’s natural immunity or immunity provided by vaccines.Our immune system has Large number of weapons For familiar bacteria, most re-infections may be milder than the first time.

However, even before these new variants came out, there were recorded cases of reinfection, including case The symptoms worsened for the second go-around. The findings of this new study still show that reinfection occurs even rarely. Therefore, no one would think that they would survive the early infection and without any problem think that they would not be infected with covid-19.Ultimately, the best way to keep everyone away from covid-19 is to vaccinate as many people as possible, including those who are already infected., According to Lowy. Compared with natural infections, the risk of this therapy is much smaller.

He said: “People who have recovered from covid-19 should still plan to be vaccinated when they have the opportunity.”

The NCI plans to continue to fund research to track the prevalence of reinfection among the general population, and to study how our immune response to the virus changes over time and research on new mutations.


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