The study, which is based on the health records of more than 5.6 million people treated at the VA Health System, found that, compared with those with only one Covid-19 infection, those with two or more documented infections had more than double the risk. of death and triple the risk of being hospitalized within six months of their last infection. They also had higher risks of lung and heart problems, fatigue, digestive and kidney disorders, diabetes and neurological problems.
BA.5 carries key mutations that help it escape antibodies made by both vaccines and previous infections, leaving many people vulnerable to reinfection.
“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-Aly said. However, this is no longer true.
“So we asked a simple question that if you’ve had Covid before and now you’re on your second infection, does that really add to the risk? And the simple answer is yes.”
Calculation of reinfection risks
Al-Aly and his team compared the health records of more than 250,000 people who had tested positive for Covid-19 once with data from another 38,000 who had two or more Covid-19 infections documented in their records. their medical. More than 5.3 million people with no record of a Covid-19 infection were used as a control group.
Among those with reinfection, 36,000 people had two Covid-19 infections, approximately 2,200 had been infected with Covid-19 three times and 246 had been infected four times.
Common new diagnoses after reinfections included chest pain, abnormal heart rhythms, heart attacks, inflammation of the heart muscle or sac around the heart, heart failure and blood clots. Common lung issues included shortness of breath, low blood oxygen, lung disease and fluid accumulation around the lungs, Al-Aly said.
The study found that the risk of a new health problem was highest around the time of a Covid-19 reinfection, but it also persisted for at least six months. The increased risk was present whether or not someone was vaccinated, and it was graded — meaning it increased with each subsequent infection.
Al-Aly said this is not what people think will happen when they get Covid for the 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’re getting it again, maybe it doesn’t affect you as much, but that’s not so. really, really,” he said.
Al-Aly 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 lasting health problems during a second infection than during their first infection, he said, they still face a 50% greater risk of problems than someone who did not contract Covid. -19 a. The second time.
The study has some important caveats. Al-Aly says it was more common to see reinfections among people who had pre-existing risks due to their age or health. This indicates that reinfection may not be random and it may be that the health risks associated with reinfections are not as well.
“It is possible that sicker individuals or people with immune dysfunction are at higher risk of reinfection and adverse health outcomes after reinfection,” Al-Aly said.
He was not interested in trying to isolate the pure effects of reinfection, but wanted to understand how repeated infections are affecting the people who get them.
“The most important question for people’s lives is, if you get re-infected, does it increase your risk of acute complications and long-term Covid, and the answer is clearly yes and yes,” he said.
The study is observational, which means it cannot determine cause and effect.
Al-Aly 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 before getting Covid-19.
Covid-19 continues to surprise
Experts who were not involved in the research say it is compelling.
“There’s this idea that I think a lot of people have that ‘if I survive my first infection, I’ll be really good the second time around. There really shouldn’t be any problem,'” said Dr. Daniel Griffin, an instructor in clinical medicine at Columbia University.
“The popular belief, isn’t it, is that reinfections are easy, nothing to worry about, nothing to see here,” Griffin said of the study on the “This Week in Virology” podcast. But that’s not really being proven, he said.
This is not how it should work. Even when viruses change form—as the flu does—our immune system generally retains its memory of how to recognize and fight some parts 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 keep us from serious harm.
With coronaviruses, and especially SARS-CoV-2 coronaviruses, the hits just keep on coming.
“A year later, you can be reinfected with the same coronavirus a second time. It’s not clear that that second infection can be milder, because coronaviruses inherently have the ability to interfere with life-long immunity,” said Griffin for CNN.
Griffin says he’s seen re-infections of Covid-19 go both ways. Sometimes, the second or third is gentler on his patients, but sometimes it isn’t.
How does this compare to other respiratory infections?
At the beginning of the pandemic, people would get Covid and it would be three months before they were sufficiently protected, he said. But now, those reinfections are happening more often, no doubt because of the rapid changes in the virus. He says he has seen some people infected four times in the past two years.
“We 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 truly 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. All of them tested positive within 72 hours of that restaurant visit.
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 that’s the reality. We’re seeing this resurgence and we’re seeing an increasing number of vaccine failures. Obviously, that’s a big concern,” he said.
CNN Health’s Deidre McPhillips contributed to this report.