The evidence is increasing COVID-19 may not protect against reinfection with some of the new variants. People can also get a second infection with earlier versions of the coronavirus if they build weak defenses the first time, new research suggests.
How long the immunity to natural infection lasts is one of the big questions at the pandemic. Scientists still think re-infections are quite rare and usually less severe than the first, but recent developments around the world have given rise to concern.
In South Africa, a vaccine study found new infections with a variant in 2% of people who previously had an earlier version of the virus.
Several similar cases were documented in Brazil with a new variant there. Researchers are investigating whether reinfections could help explain a recent rise in the city of Manaus, where three-quarters of residents would have been previously infected.
In the United States, a study found that 10% of marine recruits who had evidence of a previous infection and repeatedly tested negative before starting basic training were later infected again. That 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.
“Previous infection does not give you free passage,” he said. “There remains a significant risk of reinfection.”
Re-infections are a public health problem, not just a personal one. Even in cases where reinfection causes no or only mild symptoms, people can still spread the virus. That’s why health officials are pushing for vaccination as a longer-term solution, encouraging people to wear masks, keep physical distance, and wash their hands often.
“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,” said Dr. Anthony Fauci, the US government’s top infectious disease expert.
“My view of the data suggests … and I want to underline suggests … the protection provided by a vaccine may be even a little better” than natural infection, Fauci said.
On CBS ‘”Face the Nation” on Sunday, Dr. Scott Gottlieb, a former commissioner of the US Food and Drug Administration who sits on the board of vaccine developer Pfizer, said the vaccines would likely be less effective against the South African and Brazilian variants, but he thought the vaccines offered “reasonable protection” against the variants.
“We may also be able to develop a consensus strain in a timely manner, perhaps within four to six months, that will bind many of the different variations that we are seeing with fall boosters, so I think there is a fair chance we stay ahead of this virus while it mutates, ”said Gottlieb.
Doctors in South Africa began to worry when they saw a wave of cases late last year in areas where blood tests suggested many people already had the virus.
Until recently, all evidence was “that a previous infection provides protection for at least nine months,” so a second wave should have been “relatively subdued,” said Dr. Shabir Madhi from the University of the Witwatersrand 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% of new cases in South Africa and has spread to 40 countries including the United States.
Madhi led a study testing Novavax’s vaccine and found it less effective against the new variant. The study also found that infections with the new variant were just as common in people who had COVID-19 as they were in those who didn’t.
“What this basically tells us is, unfortunately, that earlier infection with early variants of the virus in South Africa does not protect against the new ones,” he said.
Reuters / Henry Nicholls
In Brazil, a spike in hospital admissions in Manaus in January caused similar concerns and revealed a new variant that is also more contagious and less vulnerable to some treatments.
“Reinfection could be one of the causes of these cases,” said Dr. Ester Sabino of the University of Sao Paulo. She wrote an article in Lancet magazine about possible explanations. “We have not yet been able to determine how often this happens,” she said.
Scientists in California are also investigating whether a recently identified variant may be causing re-infections or an increase in cases there.
“We’re looking at that now,” looking for blood samples from previous cases, said Jasmine Plummer, an investigator at Cedars-Sinai Medical Center in Los Angeles.
Dr. Howard Bauchner, editor of the Journal of the American Medical Association, said it would soon report on what he called the “Los Angeles variant.”
New variants weren’t responsible for the reinfections seen in the Marines study – it was done before the mutant viruses showed up, said Sealfon, who led that work with the Naval Medical Research Center. Other study findings were published in the New England Journal of Medicine; the new ones about reinfection are posted on a research website.
The study involved several thousand marine recruits who tested negative for the virus three times during a two-week supervised military quarantine before starting basic training.
Of the 189 whose blood tests indicated they were infected in the past, 19 retested positive during the six weeks of training. That’s far less than those with no previous infection – “nearly half of them got infected at the base training 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 reinfections caused serious illness, but that doesn’t mean the recruits were not at risk of spreading infection to others, Sealfon said.
“It appears that reinfection is possible. I don’t think we fully understand why that is and why immunity has not developed” in those cases, said an immunology expert with no role in the study, E. John Wherry of the University. from Pennsylvania.
“Natural infections can leave behind a range of immunity,” while vaccines consistently elicit high levels of antibodies, Wherry said.
“I’m optimistic that our vaccines are doing a little bit better.”