There is growing evidence that COVID-19 may not protect against re-infection with some of the new variants. People can also get secondary infections with previous versions of the coronavirus if they’ve built up weak defenses the first time, new research shows.
How long the immunity to natural infections lasts is one of the big questions in the pandemic. Scientists still believe that reinfections are quite rare and usually less severe than the first, but recent developments around the world have raised concerns.
In South Africa, a vaccine study found new infections with a variant in 2 percent of people who previously had a previous version of the virus.
Several similar cases with a new variant were documented in Brazil. Researchers are investigating whether reinfections help explain a recent surge in the city of Manaus, where three-quarters of residents are believed to have been previously infected.
It’s an incentive to do what we’ve been saying all along: vaccinate as many people as possible and do it as soon as possible.
In the United States, a study found that 10 percent of Marine recruits who had signs of previous infection and who tested negative repeatedly before starting basic training were later reinfected. That work was done before the new variants began to spread, said a study director, Dr. Stuart Sealfon of the Icahn School of Medicine on Mount Sinai in New York.
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“A previous infection doesn’t give you a free pass,” he said. “There is still a significant risk of re-infection.”
Better vaccination protection?
Reinfections are a public health problem, not just a personal one. Even in cases where re-infection causes no or mild symptoms, people can still spread the virus. Because of this, health officials are calling for vaccination as a longer-term solution and encouraging people to wear masks, stay physically away, and wash their hands frequently.
“It is an incentive to do what we have been saying all along: vaccinate as many people as possible and do it as soon as possible,” said Dr. Anthony Fauci, the US Government’s foremost infectious disease expert.
“My look at the data suggests … and I want to underline that … the protection induced by a vaccine may even be a little better” than a natural infection, Fauci said.
Doctors in South Africa began to worry when they saw a spate of cases late last year in areas where blood tests indicated that many people already had the virus.
Until recently, all signs were “that previous infection would provide protection for at least nine months,” so a second wave should have been “relatively subdued,” said Dr. Shabir Madhi from the Witwatersrand University in Johannesburg.
Scientists discovered a new version of the virus that is more contagious and less susceptible to certain treatments. It now causes more than 90 percent of all new cases in South Africa and has spread to 40 countries including the USA.
Madhi conducted a study testing Novavax’s vaccine and found it to be less effective against the new variant. The study also found that infections with the new variant were just as common in people with COVID-19 as in people without COVID-19.
“Unfortunately, this basically tells us that a previous infection with early variants of the virus in South Africa does not protect against the new one,” he said.
In Brazil, an increase in Manaus hospital stays in January caused similar concerns, revealing a new variant that is also more contagious and less prone to some treatments.
“Reinfection could be one of the drivers of these cases,” said Dr. Ester Sabino from the University of Sao Paulo. She wrote an article in the Lancet magazine about possible explanations. “We haven’t yet been able to define how often this happens,” she said.
California scientists are also investigating whether a recently identified variant could cause new infections or a spate of cases there.
“We’re looking into that now,” said Jasmine Plummer, a researcher at Cedars-Sinai Medical Center in Los Angeles, looking for blood samples from previous cases.
Dr. Howard Bauchner, editor-in-chief of the American Medical Association Journal, said it would soon be reporting on what he called “the Los Angeles variant.”
New variants weren’t responsible for the reinfections seen while examining Marines – this happened before the mutant viruses showed up, said Sealfon, who led the work with the Naval Medical Research Center. Additional results from the study were published in the New England Journal of Medicine. The new ones for re-infection will be published on a research website.
The study involved several thousand Marine recruits who tested negative for the virus three times during a two-week monitored military quarantine before starting basic training.
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Of the 189 whose blood tests showed they had been infected in the past, 19 tested positive again during the six-week training period. That is far less than without prior infection – “almost half of them were infected at the primary school site,” Sealfon said.
The amount and quality of antibodies previously infected Marines had on arrival was linked to their risk of getting the virus again. No re-infections caused serious illnesses, but that doesn’t mean the recruits weren’t at risk of passing infections on to others, Sealfon said.
“It looks like a new infection is possible. I don’t think we fully understand why this is and why immunity has not developed, ”said E. John Wherry of the University of Pennsylvania, an immunologist with no role in the study.
“Natural infections can induce a range of immunities,” while vaccines induce high levels of antibodies consistently, Wherry said.
“I’m optimistic that our vaccines are doing a little better.”