Covid-19 reinfections can increase the likelihood of new health problems

The study, based on the medical records of more than 5.6 million people treated in the VA healthcare system, found those with two or more documented infections had more than double the rate compared to those with just one Covid-19 infection were at risk of dying and three times as likely to be hospitalized within six months of their last infection. They were also at higher risk of lung and heart problems, fatigue, digestive and kidney disease, diabetes and neurological problems.

BA.5 carries key mutations that help it evade antibodies generated 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’d tell you I might have a patient here or there, but it’s really, really rare,” Al-Aly said. But that’s no longer true.

“So we asked a simple question: if you have previously contracted Covid and now you have your second infection, does that really increase the risk? And the simple answer is that it is.”

Counting the risks of reinfection

Al-Aly 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 documented two or more Covid-19 infections in their medical records. More than 5.3 million people with no evidence of Covid-19 infection served as a control group.

Among those with reinfections, 36,000 people had two Covid-19 infections, about 2,200 had been infected with Covid-19 three times, and 246 had been infected four times.

Frequent new diagnoses after reinfection were chest pain, cardiac arrhythmias, heart attacks, inflammation of the heart muscle or pericardium, heart failure and blood clots. Common lung problems included shortness of breath, low blood oxygen levels, lung disease and fluid buildup around the lungs, Al-Aly said.

The study found that the risk of developing a new health problem was highest at the time of Covid-19 reinfection, but also lasted for at least six months. The increased risk was present regardless of whether someone was vaccinated or not, and it was graded – that is, it increased with each subsequent infection.

Al-Aly said people don’t really believe this is going to happen if 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 it might not affect you as much, but it’s not really true,” he said.

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Al-Aly said that doesn’t mean there aren’t people who have had Covid and are fine; there are many of them. Rather, his study shows that every infection carries a new risk, and that risk adds up over time, he said.

Even if a person is at half the risk of developing lasting health problems during a second infection than they were with their first infection, they still have a 50% greater risk of problems than someone who didn’t get Covid-19 a second Times.

The study has some important caveats. Al-Aly says reinfections were more common among people who were at risk because of their age or underlying health. This shows that reinfection may not be accidental, and It could be that the health risks associated with reinfections are not, either.

“It’s possible that sicker individuals or people with immune dysfunction are at greater risk of reinfection and adverse health outcomes after reinfection,” Al-Aly said.

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He wasn’t interested in isolating the pure effects of reinfection, but wanted to understand how repeated infections affect the people who get them.

“The most important question for people’s lives is whether reinfection increases the risk of acute complications and long covid, and the answer is a resounding yes and yes,” he said.

The study is an observational study, meaning cause and effect cannot be established.

Al-Aly says the researchers saw these increased risks even after weighting the data to account for the effects of age, gender, medication use and the person’s underlying health before they got Covid-19.

Covid-19 continues to surprise

Experts not involved in the research say it’s compelling.

“There’s this notion that I think a lot of people think, ‘if I survive my first infection, I’ll be really good the second time. There really shouldn’t be a problem,'” said Dr. Daniel Griffin, associate professor of clinical medicine at Columbia University.

“The common wisdom, right, is that reinfections are mild, don’t worry about not seeing anything here,” Griffin said of the study on the This Week in Virology podcast. But that’s not really confirmed, he said.

The search for longer-lasting Covid-19 vaccines

It’s not supposed to work that way. Even when viruses change shape—like the flu does—our immune system generally retains its memory of how to recognize and fight off a portion of them. They can still make us sick, but the idea is that our previous immunity is there to build some sort of defense and protect us from serious harm.

When it comes to coronaviruses and especially SARS-CoV-2 coronaviruses, the hits just keep coming.

“A year later, you can get infected a second time with the same coronavirus. It’s not clear if this second infection can be milder because coronaviruses have the inherent ability to compromise long-lasting lifelong immunity,” Griffin told CNN.

Griffin says he’s seen Covid-19 reinfections go both ways. Sometimes the second or third is milder for their patients, sometimes not.

How does this compare to other respiratory infections?

At the start of the pandemic, people would get Covid and three months would go by where they were pretty well protected, he said. But now these reinfections are occurring more frequently, no doubt due to the rapid changes in the virus. He says he has seen some people get infected four times in the past two years.

“We don’t really see that much with the flu,” Griffin said.

What people should do about this risk now, says 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. But that doesn’t mean 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 tested positive within 72 hours of that restaurant visit.

If you’re at higher risk for serious illnesses or just want to avoid getting sick, it’s a good time to wear an N95 mask in public places, 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. It’s clearly a big problem,” he said.

CNN Health’s Deidre McPhillips contributed to this report.

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