Repeated infection with Covid-19 appears to increase a person’s chances of experiencing new and sometimes permanent health problems after being infected, according to the first study on the health risks of re-infection.
The study, which was based on the health records of more than 5.6 million people treated in the VA health care system, found that compared to those with one Covid-19 infection, those with two or more documented infections had more twice the risk of death and three times the risk of hospitalization within six months of their last infection. They also had a higher risk of lung and heart problems, fatigue, digestive and kidney disorders, diabetes and neurological problems.
The findings come after a new wave of coronavirus variants, particularly Omicron’s BA.5, became dominant in the United States and Europe, causing a renewed surge in cases and hospitalizations. BA.5 caused about 54 percent of cases nationwide last week, doubling its share of Covid-19 transmission in the past two weeks, according to data released Tuesday by the U.S. Centers for Disease Control and Prevention.
BA.5 carries key mutations that help it avoid antibodies generated by both vaccines and previous infection, leaving many people vulnerable to reinfection.
Dr. Ziyad Al-Ali, a clinical epidemiologist at Washington University in St. Louis, led the study, which was published as a preprint before peer review. He said he decided to do so after watching re-infections become more common among his own patients.
“If you asked me about reinfection maybe a year and a half ago, I would have told you maybe I have a patient here or there, but it’s really, really rare,” Al-Ali said. However, this is no longer true.
“So we asked a simple question that if you’ve had Covid before and now you’re in your second infection, does that really add risk?” And the simple answer is that it does.
Al-Ali and his team compared the health records of more than 250,000 people who tested positive for Covid-19 once with the records of 38,000 others who had two or more Covid-19 infections documented in their medical records. files. More than 5.3 million people without evidence of Covid-19 infection were used as a control group.
Among those with repeated infections, 36,000 people had two Covid-19 infections, approximately 2,200 caught Covid-19 three times, and 246 were infected four times.
Common new diagnoses after repeated infections include chest pain, abnormal heart rhythm, heart attacks, inflammation of the heart muscle or the sac around the heart, heart failure and blood clots. Common lung problems include shortness of breath, low blood oxygen, lung disease and fluid buildup around the lungs, Al-Ali said.
The study found that the risk of a new health problem was highest around the time of re-infection with Covid-19, but also continued for at least six months. The increased risk was present regardless of whether someone was vaccinated or not, and was graded—meaning it increased with each subsequent infection.
Al-Ali said this is not what people really think will happen when they get Covid a second or third time.
“There’s this idea that if you’ve had Covid before, your immune system is trained to recognize it and is better equipped to fight it, and if you get it again, maybe it doesn’t affect you as much, but it’s not really true,” he said.
Al-Ali said that doesn’t mean there aren’t people who have had Covid and done well; there are many of them. Rather, what his study shows is that each infection carries a new risk, and that risk increases over time, he said.
Even if a person has half the risk of developing permanent health problems during a second infection than they did with their first infection, he said, they’re still 50 percent more likely to have problems than someone who hasn’t got Covid-19 a second time.
The study has some important caveats. Al-Ali says reinfection is more common among people who had pre-existing risks due to age or underlying health. This indicates that re-infection may not be random and it may be that the health risks associated with re-infections are not either.
“It is possible that sicker individuals or those with immune dysfunction are at higher risk of reinfection and adverse health outcomes after reinfection,” Al-Ali said.
He wasn’t interested in trying to isolate the pure effects of reinfection, but he wanted to understand how repeated infections affect the people who get them.
“The most relevant question for people’s lives is, if you get re-infected, does that increase your risk of acute complications and prolonged Covid, and the answer is a clear yes and yes,” he said.
The study is observational, meaning it cannot determine cause and effect.
Al-Ali says the researchers saw these increased risks even after weighting the data to account for the effects of age, sex, medication use and the person’s underlying health conditions before they got Covid-19.
Experts who weren’t involved in the research say it’s compelling.
“I think a lot of people have this idea that ‘if I survive my first infection, I’m really going to be fine the second time around.’ There really shouldn’t be any problem,” said Dr. Daniel Griffin, an instructor of clinical medicine at Columbia University.
“The popular wisdom, right, is that re-infections are mild, nothing to worry about, nothing to see here,” Griffin said of the study on the “This Week in Virology” podcast. But this is not actually confirmed, he said.
This should not work. Even when viruses change form—as the flu does—our immune system usually retains its memory of how to recognize and fight off some of them. They can still make us sick, but the idea is that our previous immunity is there to create some sort of defense and protect us from serious damage.
With coronaviruses, and especially with SARS-CoV-2 coronaviruses, the hits keep coming.
“A year later, you can re-infect yourself with the same coronavirus a second time. It’s not clear whether this second infection could be milder because coronaviruses essentially have the ability to interfere with long-lasting immunity throughout life,” Griffin told CNN.
Griffin says he’s seen re-infection with Covid-19 go both ways. Sometimes the second or third is easier for his patients, but sometimes it isn’t.
How does this compare to other respiratory infections?
At the beginning of the pandemic, people will get sick with Covid and it will be three months when they will be pretty well protected, he said. But now these reinfections are happening more often, no doubt because of the rapid changes of the virus. He says he has seen some people infected four times in the past two years.
“We really don’t see a lot of that with the flu,” Griffin said.
As for what people should do now about this risk, Dr. Michael Osterholm, who directs the Center for Infectious Disease Research and Policy at the University of Minnesota, says Americans are really done with the pandemic. However, this does not mean that the pandemic is over with us.
Osterholm said he has three close friends who recently went to a restaurant for the first time since the pandemic began. They all tested positive within 72 hours of visiting the restaurant.
If you’re at higher risk of serious illness or just want to avoid getting sick, it’s a good time to wear an N95 mask in public, he says.
“People don’t want to hear it, but it’s the reality. We are seeing this resurgence and we are seeing an increasing number of failed vaccines. Obviously, that’s a big concern,” he said.