Covid-19 reinfections can bring some new risks of serious medical problems, hospitalization and death, a new study has found.
Protection provided by vaccines and prior infection has greatly improved Covid outcomes since the pandemic’s early days, and reinfections are typically less severe than initial ones. Yet each new infection carries a risk of medical problems, including hospitalization, death and long Covid, according to preliminary data from a study of patients in the Veterans Affairs health system.
This is a timely finding, doctors say, as more-infectious Omicron sub variants BA.4 and BA.5 proliferate and are expected to make reinfections more common.
The VA research is the first to look at reinfections in a significantly way, says Eric J. To pol, founder and director of Scrips Research Translational Institute, a biomedical research facility in La Jolla, Calif. “These are really large samples, and they have good statisticians,” he adds.
Covid reinfections may deal a less-harsh blow than initial ones, but each infection creates some new opportunity for the virus to damage your body, the study found. So over time, your cumulative risk of developing problems rises with each infection.
The risk of developing medical issues such as lung and heart problems is most acute in the first 30 days after an infection. Those risks remain elevated for up to six months for most conditions, and increase with each subsequent infection. For instance, out of 100 people with a reinfection and 100 who had only one infection, five more people with a reinfection developed a lung or respiratory issue or heart problem within a six-month period.
“Reinfection may be milder, but it still adds risk,” says Zad Ally, chief of research and development at the VA St. Louis Health Care System and a clinical epidemiologist at Washington University in St. Louis, who led the study.
The researchers compared the electronic health records of three groups of people: more than 257,000 people with one confirmed Covid-19 infection; more than 38,900 people with two or more infections; and a control group of more than 5.3 million who didn’t have a Covid-19 infection. The majority of those with reinfections—92%—had two infections. The study hasn’t yet been peer-reviewed and is under review for publication.
One caveat of the VA study is that their patients are older and tend to have multiple comorbidities, says Amesh A. Adalja, a senior scholar at Johns Hopkins Center for Health Security, who wasn’t involved with the VA study. For instance, an otherwise healthy 18-year-old “is not likely to significantly add to their risk” in the same way as an older person with underlying health problems, says Dr. Adalja.
And VA patients who went to the doctor for a reinfection are also more likely to have had more symptoms than those who don’t seek medical care and aren’t captured in the study, Dr. Adalja notes.
Still, “it’s better not to get reinfected than to be reinfected,” he says. “Reinfections are not something you want to have, even though they’re likely going to be ubiquitous.”
With the more contagious and immune-evading Omicron subvariants BA.4 and BA.5, reinfections matter because they will become more common, according to Dr. Topol.
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