If you’ve had COVID, it’s pretty certain you really don’t want to get it again. You may think that having had it will protect you, but that is not true. People can get COVID a second, third or even fourth time. And each reinfection raises the likelihood a person will be hospitalized or develop a disorder or disorders affecting the lungs, heart, brain, or the blood, musculoskeletal and gastrointestinal systems. And with winter and flu season coming on, the risk of infection is growing.

Having repeat SARS-CoV-2 infections add significant additional risk to multiple organ systems, researchers at Washington University School of Medicine in St. Louis and the Veterans Affairs St. Louis Health Care system found. Reinfection can also contribute to diabetes, kidney disease and mental health issues.

As the U.S. heads into the winter months, limiting exposure to the virus is especially important with new variants emerging, mutating and already causing rising rates of infection in parts of the country.

“Without ambiguity, our research showed that getting an infection a second, third or fourth time contributes to additional health risks in the acute phase, meaning the first 30 days after infection, and in the months beyond, meaning the long COVID phase,” senior author, Ziyad Al-Aly, MD, a clinical epidemiologist at the School of Medicine, said in a statement.

People who have had COVID-19 or been vaccinated and boosted may feel they are invincible, and have “a sort of superimmunity to the virus,” he added. That is not what the researchers found, however.

Instead, the epidemiolgists discovered that people with COVID-19 reinfections were twice as likely to die and three times more likely to be hospitalized than those with no reinfection.

The findings are based on information from the de-identified medical records of nearly 5.8 million patients from a database maintained by the U.S. Department of Veterans Affairs. Patients represented multiple ages, races and sexes. From this group the researchers selected a data set of 5.3 million people who did not test positive for COVID-19 infection from March 1, 2020, through April 6, 2022.

They also gathered the records of a group of more than 443,000 people who had tested positive for one COVID-19 infection during the same time frame to serve as a control group. From this control group, they compiled another group of nearly 41,000 people who had two or more documented infections. Most people in this multiply-infected group had had two or three infections, with a small number having had four infections. No one had five or more infections.

Next, the researchers used statistical modeling to examine the health risks of repeat COVID-19 infections within the first 30 days after contracting the virus and up to six months after. Using these statistical techniques, the team examined the health risks of repeat COVID-19 infections within the first 30 days after contracting the virus and up to six months after.

COVID-19 variants such as delta, omicron and BA.5 were all included in the analysis.

“We really need to do our best to reduce the chance we will have a twin-demic of both COVID-19 and the flu this winter season.”

Overall, that people with COVID-19 reinfections were twice as likely to die and three times more likely to be hospitalized than those with no reinfection, the researchers found. Negative outcomes occurred among the unvaccinated as well as those who had received shots prior to reinfection.

People who had repeat infections were 3.5 times more likely to develop lung problems, three times more likely to suffer heart conditions and 1.6 times more likely to experience brain conditions than patients who had been infected with the virus once.

Hopefully, the findings will serve as a wake-up call for those people who feel they are immune to the threat of COVID-19. “Going into the winter season, people should be aware of the risks and practice vigilance to reduce their risk of infection or reinfection with SARS-CoV-2,” Al-Aly said.

As the U.S. heads into the winter months, limiting exposure to the virus is especially important with new variants emerging, mutating and already causing rising rates of infection in some parts of the country, he added. “People should do their best to prevent repeat infections by masking, for example, getting all of their eligible boosters, staying home when sick. Also, get a flu shot to prevent illness. We really need to do our best to reduce the chance we will have a twin-demic of both COVID-19 and the flu this winter season.”

The study is published in Nature Medicine.