The study, which is based on the health records of more than 5.6 million people treated in the VA healthcare system, found that compared to those who had just one Covid-19 infection , those with two or more documented infections were more than twice as likely to die and three times as likely to be 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 evade antibodies generated by both vaccines and previous infection, leaving many people vulnerable to reinfection.
“If you had asked me about reinfection maybe a year and a half ago, I would say to you that I may have a patient here or there, but it’s really, really rare,” said said Al-Aly. This is no longer true, however.
“So we asked a simple question: if you’ve already had Covid and are now on your second infection, does that really add risk? And the simple answer is that it does.”
Accounting for the risks of reinfections
Al-Aly and his team compared the health records of more than 250,000 people who had tested positive for Covid-19 once with the records of another 38,000 who had two or more documented Covid-19 infections in their records. medical. More than 5.3 million people with no history of Covid-19 infection were used as a control group.
Of those who were re-infected, 36,000 people had two Covid-19 infections, around 2,200 had caught 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 the sac around the heart, heart failure and blood clots. Common lung problems included shortness of breath, lack of oxygen in the blood, lung disease and fluid buildup around the lungs, Al-Aly said.
The study found that the risk of a new health condition was highest at the time of reinfection with Covid-19, but also persisted for at least six months. The increased risk was present whether someone had been vaccinated or not, and it was graded, meaning it increased with each subsequent infection.
Al-Aly said that’s not what people really think will happen when they have 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 more equipped to fight it, and if you get it again, maybe it doesn’t affect you as long as that, but that’s not really true,” he said.
Al-Aly said that doesn’t mean there aren’t people who have had Covid and have done very well; There are many. Rather, what his study shows is that with every infection comes a new risk, and that risk adds up over time, he said.
Even though a person is half as likely to develop lasting health problems with a second infection as they were with their first infection, he said, they still end up with 50% more chance of problems than their first infection. a person who has not contracted Covid-19 has a second time.
The study has some important caveats. Al-Aly says it was more common to see reinfections in people who had existing risks due to their age or underlying medical condition. This shows that reinfection may not be random, and neither might the health risks of reinfections be.
“It is possible that the sickest people or people with immune dysfunction are at higher risk of reinfection and adverse health effects after reinfection,” Al-Aly said.
He wasn’t interested in trying to isolate the pure effects of reinfection, but wanted to understand how repeated infections affect the people who get them.
“The question most relevant to people’s lives is whether you get re-infected, does that increase your risk of acute complications and long Covid, and the answer is clearly yes and yes,” he said. declared.
The study is observational, meaning it cannot determine cause and effect.
Al-Aly says the researchers saw these increased risks even after weighting the data to take into account the effects of the person’s age, gender, medication use and underlying health before that. she does not catch Covid-19.
Covid-19 continues to surprise
Experts who weren’t involved in the research say it’s compelling.
“There’s this idea that I think a lot of people have that ‘if I survive my first infection, I’ll be really fine the second time around. There really shouldn’t be a problem,'” Dr. Daniel said. Griffin, instructor in clinical medicine at Columbia University.
“The conventional wisdom, on the right, is that reinfections are benign, there’s 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 confirmed, he said.
That’s not how it should work. Even when viruses change shape – like 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 mount some sort of defense and prevent us from taking serious damage.
With coronaviruses, and in particular SARS-CoV-2 coronaviruses, the blows keep coming.
“A year later, you can be reinfected with the same coronavirus a second time. It’s not clear that this second infection could be milder, as coronaviruses inherently have the ability to interfere with lifelong immunity. duration,” Griffin told CNN.
Griffin says he’s seen Covid-19 reinfections go both ways. Sometimes the second or third is kinder to his patients, but sometimes it’s not.
How does this compare to other respiratory infections?
At the start of the pandemic, people were catching Covid, and three months would pass when they were pretty well protected, he said. But now these reinfections are happening more frequently, no doubt because of the rapid changes in the virus. He says he has seen infected people four times in the past two years.
“We don’t really see that with the flu,” Griffin said.
As for what people should do now about that 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 finished with us.
Osterholm said he has three close friends who recently dined out for the first time since the pandemic began. All tested positive within 72 hours of this restaurant visit.
If you’re at higher risk of serious illness or just want to avoid getting sick, now is a good time to wear an N95 mask in public places, he says.
“People don’t want to hear it, but it’s the reality. We’re seeing this resurgence, and we’re seeing an increasing number of vaccine failures. Obviously, that’s a major concern,” he said. he declares.
CNN Health’s Deidre McPhillips contributed to this report.
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