Evidence is gathering that COVID-19 may not protect against re-infection with some of the new variants. People may also get a second infection with previous versions of the coronavirus if they have weakened the first time, new research suggests.
How long the immunity from natural infection lasts is one of the big questions in the pandemic. Scientists believe that reinfections are quite rare and usually less severe than the initial ones, but recent developments around the world have raised concerns.
In South Africa, a vaccine study found new infections with a variant in 2% of people who previously had a previous version of the virus.
In Brazil, several similar cases have been documented with a new variant there. Researchers are exploring whether reinfections help explain a recent rise in the city of Manaus, where three-quarters of residents were thought to have been previously infected.
In the United States, one study found that 10% of marine recruits who had evidence of a previous infection and tested negative repeatedly before starting basic training were subsequently infected again. This work was done before the new variants began to spread, said a study leader, Dr. Stuart Sealfon of the Icahn School of Medicine at Mount Sinai in New York.
“The previous infection does not give you a free license,” he said. “There remains a substantial risk of reinfection.”
Reinfection is a public health problem, not just a personal one. Even in cases where the reinfection does not cause symptoms or only mild, people could spread the virus. That is why health officials call for vaccination as a long-term solution and encourage people to wear masks, keep their physical distance and wash their hands frequently.
“It’s an incentive to do what we say over time: vaccinate as many people as possible and do it as quickly as we can,” said Dr. Anthony Fauci, the government’s leading infectious disease expert. US.
“My look at the data suggests … and I want to emphasize suggests … vaccine-induced protection may be even a little better” than natural infection, Fauci said.
Doctors in South Africa began to worry when they saw an increase in cases late last year in areas where blood tests suggested many people already had the virus.
Until recently, all indications were “that the previous infection has provided protection for at least nine months,” so a second wave should have been “relatively low,” said Dr. Shabir Madhi of the University of the Witwatersrand in Johannesburg.
Scientists have discovered a new version of the virus that is more contagious and less susceptible to certain treatments. It now causes more than 90% of new cases in South Africa and has spread to 40 countries, including the United States.
Madhi conducted a Novavax vaccine testing study and found it less effective against the new variant. The study also found that infections with the new variant were as common in people who had COVID-19 as in those who did not.
“What it tells us, unfortunately, is that the past infection with early variants of the virus in South Africa does not protect” against the new one, he said.
In Brazil, an increase in hospitalizations in Manaus in January caused similar concerns and revealed a new variant, which is also more contagious and less vulnerable to some treatments.
“Reinfection could be one of the determining factors in these cases,” said Dr. Ester Sabino of the University of Sao Paulo. She wrote an article in the Lancet magazine about possible explanations. “We have not yet been able to define how often this happens,” she said.
Scientists in California are also investigating whether a recently identified variant can cause reinfections or a wave of cases there.
“We’re looking at this now,” looking for blood samples from past cases, said Jasmine Plummer, a researcher at Cedars-Sinai Medical Center in Los Angeles.
Dr. Howard Bauchner, editor-in-chief of the Journal of the American Medical Association, said he would soon report what he called the “Los Angeles version.”
The new variants were not responsible for the reinfections observed in the Marines study – it was done before the appearance of the mutated viruses, said Sealfon, who led that collaboration with the Naval Medical Research Center. Other findings of the study were published in the New England Journal of Medicine; the new ones about reinfection are posted on a research site.
The study involved several thousand Marine recruits who tested negative for the virus three times during a two-week supervised military quarantine before basic training began.
Of the 189 whose blood tests indicated they had been infected in the past, 19 were positive again in the six weeks of training. It’s much less than those without a previous infection – “almost half of them became infected at the basic training site,” Sealfon said.
The amount and quality of antibodies that previously infected sailors had on arrival were related to the risk of contracting the virus again. No re-infection has caused serious illness, but that doesn’t mean recruits aren’t at risk of spreading the infection to others, Sealfon said.
“It seems that reinfection is possible. I don’t think we fully understand why this is happening and why immunity has not developed, ”said E. John Wherry, an expert in immunology without a role in the study.
“Natural infections can leave you with a number of immunities” while vaccines constantly induce high levels of antibodies, said Wherry.
“I’m optimistic that our vaccines are doing a little better.”
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