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For those who catch COVID-19 more than once, each reinfection may increase the risk of health complications, according to a new study published as a preprint.
The increased risks were seen in both unvaccinated and vaccinated individuals, including those who had gotten a booster dose, study authors from the Washington University School of Medicine and VA Saint Louis Health Care System wrote in their research, which is currently under review by Nature Portfolio, published June 17.
The work, titled “Outcomes of SARS-CoV-2 Reinfection,” found that after every COVID-19 reinfection, there was a higher risk of death, hospitalization and lasting health consequences from the virus, including on the lungs and throughout the body, according to the study.
“Risks were lowest in people with 1 infection, increased in people with 2 infections, and highest in people with 3 or more infections,” authors wrote after setting out to address whether reinfections add to “health risks associated” with an initial infection.
Researchers believe the work is the first to fully “characterize” reinfection risks.
In the work, electronic health records from the U.S. Department of Veteran Affairs were examined, including records of 257,427 people infected with COVID-19 for the first time, 38,926 people who were reinfected and 5,396,855 people who were not known to be infected.
Of those reinfected, more than 36,000 had COVID-19 twice, more than 3,000 had been infected three times and more than 200 had been infected four or more times, according to the study.
COVID-19 reinfections can occur quickly regardless of vaccination status, McClatchy News previously reported. In one case, a health care worker, who was vaccinated and boosted, tested positive for the virus 20 days after their first infection, according to researchers in Spain.
In this recent study, the results “should not be considered conclusive” as they are “preliminary,” according to a written note included at the top of the report.
Dr. Aubree Gordon, who was not involved in the study and is an associate professor of epidemiology at the University of Michigan’s School of Public Health, told McClatchy News that the study “merits more research being done.”
“We need to understand more about the risks of reinfection.”
Reinfection health risks
In the study, those who tested positive for COVID-19 at least once did so during March 1, 2020 and Sept. 4, 2021. This is before the omicron variant, the current dominant version of the virus in the U.S., is known to have begun spreading across the country.
Those considered reinfected tested positive “more than 30 days after the first infection” but within six months, according to the work. Researchers followed up with all study participants until April 4, 2022.
Of those who had been reinfected, researchers found they showed an increased risk of consequences on the lungs, as well as cardiovascular, blood clotting, gastrointestinal, kidney, neurological, musculoskeletal, and mental health disorders. Patients were also at higher risk of developing type 2 diabetes.
A major finding included how reinfection risks “were most pronounced” in the initial illness phase after an infection began, but some people saw the adverse health effects in the “post-acute” or long COVID phase, which is considered at least four weeks after an infection, according to study authors.
After analyzing the study, clinical epidemiologist Dr. Deepti Gurdasani, who is based in the U.K., wrote in a Twitter thread that “re-infections clearly can cause significant mortality and morbidity, and avoiding each infection seems to be important.”
Gordon said there are likely “significant biases” to keep in mind when looking at this study as researchers examined a “fairly specialized population” of people who also had comorbidities, including cancer, cardiovascular disease, chronic kidney disease and more, the research noted.
She added that with a “study that relies on electronic medical records” it “relies on doctors ordering tests” and “people coming in to seek care.”
The study may have been missing out on crucial data, as Gordon explained, “you always have to worry about all of the external factors that affect whether or not the doctor orders the test and also whether or not the person comes in in the first place to seek care.”
In the study, researchers acknowledged how the research did not encompass those who may have been sick with COVID-19 but never got tested.
In Gordon’s own research on COVID-19 reinfections, she found that second COVID-19 infections were “somewhat less severe” than an initial infection. She told McClatchy News that the work, which was published online as a preprint in November 2021 and is currently under review, examined unvaccinated individuals in Nicaragua.
Ultimately, she said this does not mean “that people can’t have a severe second infection.”
She added that more research is needed to get a better understanding of what reinfections look like and how severe they can be.
Study authors concluded in their research that “reducing overall burden of death and disease due to SARS-CoV-2 will require strategies for reinfection prevention.”