Most of us now view COVID-19 as more of a nuisance than a danger, thanks to vaccines and past exposure to the virus—all of which have built up our immunity.
But research suggests that multiple COVID-19 infections pose a risk for developing Long COVID. In the largest Long COVID study of young people to date, scientists led by a team at the University of Pennsylvania report that young people who got infected twice with COVID-19 were twice as likely as those who got COVID-19 once to develop Long COVID symptoms that affect major organs like the heart, kidney, and lungs, as well as taste and smell.
The ongoing research project, called RECOVER, is funded by the National Institutes of Health and explores the impact of COVID-19 infections on long-term health. Yong Chen, professor of biostatistics and director of the Center for Health AI and Synthesis of Evidence (CHASE) at the University of Pennsylvania, and his colleagues focused on people 21 and younger to better understand how COVID-19 reinfection affects health. “People think that reinfections don’t matter as much and don’t take them seriously,” Chen says. “Our primary message is that reinfections still matter, and you should do what you can to avoid reinfection by taking a vaccine or wearing a mask.”
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The study involved data collected from more than 460,000 children, adolescents, and young adults from 40 pediatric hospitals who were diagnosed with a first COVID-19 infection around January 2022; some went on to develop a second infection after that. At the end of 2023, the researchers compared the group with only one infection to the group with a second infection, focusing on Long COVID-like symptoms such as abdominal pain, respiratory distress, changes in taste and smell, fatigue, chest pain, myocarditis, or irregular heart beat.
Those who developed a second infection were more than twice as likely as the group with only one infection to get a diagnosis of Long COVID, and the reinfected people were nearly three times as likely to report changes in taste and smell as those who only had one COVID-19 infection. This risk remained regardless of whether people were vaccinated or not, or regardless of how severe their infections were.
However, “vaccination status” referred to whether people had been vaccinated before the study period—not how recently they had received the shot. (The study was also initiated before the first updated vaccines targeting Omicron were available.) The authors emphasize that the results do not suggest that vaccines do not help to reduce the risk of Long COVID. Rather, the data show that kids who were vaccinated were much less likely to get COVID-19 in the first place and were also less likely to get reinfected compared to unvaccinated children.
Getting vaccinated, Chen says, is an important first step in protecting against possible Long COVID.
However, the study shows that even if you’re vaccinated, reinfection poses a significant enough risk to double your chances of developing Long COVID compared to just getting it once.
“The message is about how seriously you should treat your potential risk of getting a second COVID-19 infection,” says Chen. These results, along with other research, suggest that there might be a cumulative harmful effect of repeat COVID-19 infections on the body, and scientists are trying to better understand those potential long-term effects. Chen is also continuing the work to study what effect getting vaccinated following a first infection might have on not just the risk of additional infections, but on the development of Long COVID as well.
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