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Every COVID-19 reinfection increases health risks

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July 7, 2022 — People who are reinfected with the virus that causes COVID-19 have greater health risks with each cycle of reinfection, a large national database study reveals.

Researchers found more severe health effects during active infection, but some symptoms lasted up to 6 months, suggesting a direct link between reinfection and long COVID.

“Reinfection adds or contributes to additional health risks. It’s not entirely benign, and people should try to avoid getting reinfected,” says study lead author Ziyad Al-Aly. , MD.

The risks remained whether people were fully vaccinated or not. In some cases, people may have been infected earlier with the Delta strain and now be exposed to Omicron or its subvariant, BA.5, which may be more effective at evading vaccine protection, he says.

“It’s also possible that the first infection weakened some organ systems and made people more vulnerable to health risks when they get a second or third infection,” adds Al-Aly, a clinical epidemiologist at the University of Washington. and head of research and development at the VA St. Louis Health Care System. “There are a lot of variables at play, but clearly reinfections contribute to additional risks and should be avoided.”

Al-Aly and colleagues compared 257,427 people with a first infection with the virus that causes COVID-19 to a group of 38,926 people who had a second or subsequent infection, and then to 5.4 million. people who have never been infected. Information for the study came from veterans in a Department of Veterans Affairs health care database.

The results were published online June 17 as a pre-print study, which means they have not yet been peer-reviewed, a key step to help assess and validate the clinical research. . The study is being reviewed by the journal Nature Wallet.

Experts weigh

Three COVID-19 experts who were not involved in the research raised some caveats, including how a study on veterans might or might not apply to the general population.

“This is the first study to characterize the risks of reinfection,” says Eric Topol, MD.

He points out that a second infection, compared to a first, was associated with twice as many people dying from any cause, as well as twice the risk of heart or lung problems.

The additional risks also increased with each infection, says Topol, executive vice president of Scripps Research and editor of Medscape, WebMD’s sister site for healthcare professionals.

“Obviously, these results are concerning because reinfection was quite rare before the Omicron wave hit, at 1% or less through the Delta variant wave. But now reinfections have become much more common,” he says. .

Higher risks, especially for some

The study was “well done,” said Ali Mokdad, PhD, when asked to comment. Al-Aly and his colleagues “have access to good data, and they have done several studies”.

He says the additional risks are more likely in the elderly, immunocompromised people and people with other health conditions.

“It makes sense, and let me explain why,” Mokdad says. “When you have someone who first got COVID-19 and was affected by it, maybe someone who was older or had a chronic illness, the next hit would also cause more damage.”

“That’s why you’d expect some people to be more likely to have a tougher second infection,” says Mokdad, adjunct professor of epidemiology and professor of health sciences at the University of Washington in Seattle.

“The best thing for you and for the general public — healthy or not, with chronic disease or not — is to not get infected,” he says. “Get your shots and boosters, and wear a mask when you’re in a crowded place and can’t keep a safe distance.”

Are veterans’ risk factors different?

“When you look at this study, the big caveat is that veterans don’t look like the general population,” says Amesh Adalja, MD, principal investigator at the Johns Hopkins Center for Health Security at the Bloomberg School of Public Health in Baltimore. .

“I don’t think we can generalize [the study] for everyone, but really for people who have risk factors for serious illness,” he says, because veterans tend to be older and have more health problems.

He says many people who are re-infected test positive at home. As a result, their cases are not investigated. In contrast, the veterans in the study were “people who for some reason wanted to take a formal test.”

Because the virus has mutated away from vaccines, the shots can still protect against serious illness, hospitalization and death, but they are less able to protect against infection, Adalja says. “This is also the case with prior immunity. If you were a BA.1 or Delta infected person, for example, your ability to repel the new variants, BA.4 and BA.5, may not be very high.”

The study shows why “it’s important to stay up to date with your vaccines,” he says, “and why we need to get better vaccines that target the variants that are currently circulating.”

Despite these caveats, says Adalja, the researchers used “a robust database” and a large study population, which “gives us all confidence in the strength of the finding.”

Examine the longer-term effects

It was unclear whether reinfection contributed to an increased risk of long COVID, so researcher Al-Aly and colleagues followed the veterans for 6 months. They compared people who had one, two, three or more infections to the uninfected group.

Of those who were reinfected, about 13% had two infections, 0.76% had three infections, and 0.08%, or 246, had four or more infections.

Compared to veterans with a first coronavirus infection, those who were reinfected had more than double the risk of dying from any cause.

Although “the mechanisms underlying the increased risk of death and adverse health outcomes upon reinfection are not completely clear,” the authors state, “the results highlight the consequences of reinfection and underscore the importance of preventing reinfection with SARS-CoV-2, ” the virus that causes COVID-19.

Asked about the next stage of their research, Al-Aly said, “BA.5 seems to be the main challenge on the horizon, and we are focused on trying to understand it better.”