Recent research indicates that re-infection with Covid-19 is more common and can occur within a shorter period of time than doctors previously thought possible. More than half of people in the United States showed signs of infection at least once as of February, According to the report Tuesday from the Centers for Disease Control and Prevention.
Data from the UK government It found that the incidence of infection was ten times higher during the recent period omicron eruption Compare with the previous delta eruption Between May and December of last year. People who were unvaccinated, were younger and lived in areas the study described as more deprived were more likely to contract infection between July 2020 and March 2022.
Doctors say that re-infection usually appears to be mild in healthy people. But some cases of re-infection are serious, and it is not clear what the risks are covid long It may be. UK data suggest that people who had a milder initial infection with a lower viral load were more likely to be infected again.
“On average at the population level, the People who get infected again “This does not mean that some people may not have a worse infection the second or even third time,” says Francois Ballou, an infectious disease epidemiologist and director of the UCL Genetic Institute in London.
Currently in the UK About 12% of Covid-19 infections are recurrent infectionsDr. Ballox says. He expects this number to increase over time and says it’s possible that the viral dose or number of particles a person is exposed to affects the severity of symptoms.
Scientists are still learning about the frequency and severity of infection; Lots of introductory research so far. The United States does not track infection rates again broadly.
Re-infections can occur in as little as three months
Doctors and health agencies typically say that most people are protected from reinfection with Covid for at least 90 days. After an injury, the body’s immune defenses usually strengthen, and then diminish.
However, there is evidence that people can become infected again within shorter periods.
that Centers for Disease Control and Prevention April report He identified 10 people who were infected again with Covid-19 less than 90 days later. In at least one case, reinfection occurred 23 days later.
Researchers in Spain recently presented preliminary results for a study Documenting the case of a 31-year-old woman who contracted Covid-19 twice in three weeks. The woman, a health care worker, was fully vaccinated and received a booster injection 12 days before she tested positive for the delta variant on December 20. She had no symptoms the first time she was infected. Twenty days later, she developed a cough and fever and tested positive for the Omicron variant.
There is also preliminary evidence that re-infection with the same variant may occur. Danish draft, a study that has not been peer-reviewed, has found that reinfection with different Omicron subvariants is rare but does occur. They found that of the 187 reinfection cases, 47 were infected with BA.1 and then BA.2 after 20 to 60 days. The vast majority of people were young, unvaccinated and had mild symptoms. There was no difference in severity between the first and second infection.
Some cases of re-infection can be dangerous
a March print Examines more than 300,000 Covid-19 patients in the US VA system. About 9,200 of them tested positive again at least 90 days after their first positive test; 17% of infected patients were hospitalized. Another 189 cases tested positive for a third at least 90 days after the second infection and about 26% of them were hospitalized.
“These data suggest that it is reasonable to be cautious about reinfection,” says Theodore Iwashina, MD, an intensive care unit physician at VA in Ann Arbor, Michigan, and first author of the initial study.
“There’s a lot of reinfection in less than 90 days,” says Mark Pandori, director of the Nevada Public Health Laboratory and assistant professor of pathology at the University of Nevada, Reno. Dr. Panduri and colleagues documented two cases that were significantly more severe the second time around.
The risk of contracting COVID-19 for a long time after reinfection is unclear
Scientists do not yet know what is the risk of developing a long-term Covid disease after infection again. Amish Adalja, MD, an infectious disease physician and senior researcher at Johns Hopkins University Center for Health Security speculates that you are less likely to catch Covid long after you get infected again — just as vaccines reduce the likelihood of contracting Covid for a long time — because your immune system activates faster the second time around. .
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“First infection is the most likely to lead to complications based on what we know about many other endemic infectious respiratory diseases,” he says.
But Amy Ducro, an infectious disease specialist at Kaiser Permanente, says many questions about Long Covid remain unanswered.
“I don’t think we should bet on someone who is infected again and has a lower probability of contracting Covid for a long time,” Dr. Ducreux says.
A research group that grew out of Body Politic Patient Support Group has begun a re-infection study with part of a $3 million grant it recently received. To study the effect of infection on Covid patients for a long time.
Gina Assaf, co-founder and co-leader of the research group, says Body Politic has heard from people who have had Covid long after being infected again. “We don’t know to what degree this is happening, but it does,” she says.
Write to Sumathi Reddy at Sumathi.Reddy@wsj.com
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