Repeated COVID infections pose significant health risks, study warns
In the first study to investigate the effects of repeat SARS-CoV-2 infections on a person's general health researchers have found COVID reinfections can increase one's risk of neurological diseases, diabetes, lung problems and heart disease. The findings suggest a second or third COVID infection could result in adverse health outcomes not seen during an initial infection.
"During the past few months, there's been an air of invincibility among people who have had COVID-19 or their vaccinations and boosters, and especially among people who have had an infection and also received vaccines; some people started to referring to these individuals as having a sort of superimmunity to the virus," explained senior author on the new study Ziyad Al-Aly.
Over the last couple of years it has become increasingly clear that COVID-19 is not just a brief respiratory disease. In the months after an infection studies have shown recovered patients are at a greater risk of heart problems, stroke, neurological disease, and diabetes.
But with the rise of Omicron, and accompanying massive waves of COVID reinfections, it is unclear whether those increased risks persist with each new infection. If you were fine after your first encounter with COVID does that mean your second or third infection will be similar?
According to Al-Aly's new research, published in Nature Medicine, each subsequent COVID infection increases a person's cumulative risk of suffering from a broad assortment of health problems.
Al-Aly is an epidemiologist at the Washington University School of Medicine in St. Louis who has been working with the US Department of Veterans Affairs for several years. His research digs into massive healthcare databases and tracks population-level effects of COVID infections.
Instead of focusing on the acute effects of SARS-CoV-2 infections Al-Aly has been interested in studying how COVID infections can increase rates of other health problems in the weeks and months after the initial disease. His prior work has found initial infections can up a person's risk of heart and brain problems for up to a year.
The new research looked at the effects of second and third COVID infections in a cohort of several million US veterans. The study built a control group of around five million non-infected subjects and compared their rates of several diseases to what is seen in a cohort of subjects with one COVID infection (around 400,000 people) and two or more infections (around 40,000 people).
"Without ambiguity, our research showed that getting an infection a second, third or fourth time contributes to additional health risks in the acute phase, meaning the first 30 days after infection, and in the months beyond, meaning the long COVID phase," Al-Aly explained. "This means that even if you've had two COVID-19 infections, it's better to avoid a third. And if you've had three infections, it's best to avoid the fourth."
The findings strikingly reveal that people on their second or third COVID infection are three times more likely to suffer from heart or kidney problems, and almost twice as likely to suffer from neurological disorders, compared to people experiencing only one COVID infection.
In general, the health risks accompanying a reinfection were highest in the 30-day period after initial infection, but some risk did persist for up to six months. And this increased risk was present regardless of a person's vaccination status.
Compared to noninfected controls, cumulative risks of repeat infection increased according to the number of infections— Ziyad Al-Aly, MD (@zalaly) November 10, 2022
Every reinfection contributes additional risk
3 infections worse than 2
2 infections worse than 1
1 infection worse than none https://t.co/RVENVKRucU pic.twitter.com/ck55k4voes
Perhaps the most important thing to understand from this new study is that a second or third COVID infection is not more dangerous than the first but instead it generates additional risk for other health problems. Looking at cumulative risk over several infections the study clearly shows a second infection increases a person's chances of detrimental outcomes, compared to someone who avoided that extra encounter with the virus.
As Al-Aly explained to CNN, this means a person on their second or third infection still faces a greater overall risk of broad health complications compared to someone only infected once. So for example, if a second infection hypothetically generates half the risk of heart complications compared to the first infection it still means a person faces a substantial increased risk following reinfection.
Ultimately Al-Aly stressed the importance of remaining vigilant in trying to avoid reinfection with SARS-CoV-2, even if your first bout with the virus was seemingly benign.
“Our findings have broad public health implications as they tell us that strategies to prevent or reduce the risk of reinfection should be implemented,” he added. “Going into the winter season, people should be aware of the risks and practice vigilance to reduce their risk of infection or reinfection with SARS-CoV-2.”
The new study was published in Nature Medicine.