Many people assume that once they’ve had COVID-19, a second or third infection will be milder or not worth worrying about. A large study led by researchers at Washington University School of Medicine in St. Louis found that each reinfection adds its own risks, including a higher chance of serious health problems and long COVID.
How the study worked
The research, published in Nature Medicine in 2022, used health records from the U.S. Department of Veterans Affairs covering March 2020 to April 2022. The team compared three groups:
- About 443,000 people who had COVID-19 once
- About 41,000 people who had two or more infections
- More than 5 million people with no recorded infection
They then looked at how often each group experienced death, hospitalization and a wide range of health problems, both in the first month after infection and in the months that followed.
What the researchers found
- Reinfection added risk on top of the first infection. People who were reinfected had a higher risk of death and hospitalization than those infected only once.
- Problems affected many body systems. Reinfection was linked to higher risks of issues involving the lungs, heart, blood clotting, kidneys, digestion, metabolism (including diabetes), nerves and mental health.
- Risks built up with each infection. The more infections a person had, the greater their cumulative risk.
- The risk lasted. The danger was highest in the first month after reinfection but remained elevated for at least six months, contributing to long COVID.
- It applied to everyone. The added risk showed up in unvaccinated, vaccinated and boosted people alike.
The study has limits. Veterans in the VA system are mostly older men, so the results may not apply equally to everyone. It also covered a period before newer variants and updated vaccines. But the main message, that reinfection isn’t harmless, is supported by other research too.
Why this matters
COVID-19 hasn’t gone away, and most people will be exposed more than once. Earlier infection and vaccination both help the immune system, and vaccination remains strongly protective against severe illness. But neither makes a person immune to the effects of catching the virus again. That’s why the researchers encouraged doctors and public health leaders to focus on preventing reinfections, not just first infections.
Because so many people have now had COVID-19 more than once, these findings apply to a large share of the population, not just a small group.
What this means for you
- Stay up to date with recommended vaccines. Updated shots help lower the risk of severe illness, even if they don’t prevent every infection.
- Use extra precautions when risk is high. During surges, consider a well-fitting mask on planes, in crowded indoor spaces and around people at higher risk.
- Improve indoor air. Opening windows, using air purifiers and gathering outdoors when possible all reduce spread.
- Test and stay home when sick. This helps protect the people around you.
- Ask about treatment early. If you’re at higher risk and test positive, antiviral medicine may lower your chance of severe illness.
- Pay attention to how you feel afterward. If symptoms linger or new problems appear in the weeks after an infection, talk with your doctor.
The bottom line
Each COVID-19 infection carries its own risks, and getting infected again can raise the chance of serious illness and long COVID, whether or not you’ve been vaccinated or infected before. Reducing your chances of reinfection is still worth the effort.
This article is for general information and isn’t medical advice. Talk with your healthcare provider about your individual needs.
