The first study on the health implications of reinfection suggests that getting Covid-19 more than once increases the likelihood that an individual will experience new, and occasionally persistent, health issues following their infection.
According to the study, which was based on the health records of more than 5.6 million patients treated in the VA Health System, people with two or more documented infections had a risk of death that was more than twice as high and a risk of being hospitalized within six months of their last infection that was three times as high. Additionally, they were more likely to experience fatigue, kidney, gut, and heart disease, diabetes, and neurological issues.
The findings come at a time when cases and hospitalizations are once again on the rise due to a new wave of coronavirus variations, most notably Omicron's BA.5. According to information released on Tuesday by the US Centers for Disease Control and Prevention, BA.5 was responsible for almost 54% of cases across the US last week, more than doubling its proportion of Covid-19 transmission over the previous two weeks.
Many people are vulnerable to reinfection because BA.5 carries crucial alterations that enable it to evade antibodies produced by both vaccinations and earlier infections.
The study was conducted by clinical epidemiologist Dr. Ziyad Al-Aly of Washington University in St. Louis, and it was published as a preprint prior to peer review. He claimed that after noticing how frequently reinfections occurred in his own patients, he made the decision to act.
A year and a half ago, if you had asked Al-Aly about reinfection, he would have replied, "I might have a case here or there, but it's really, really unusual." But that's no longer accurate.
"So, we posed the straightforward question: Does it truly increase risk if you previously contracted Covid and are currently dealing with a second infection? And the obvious response is yes, it does."
Calculating the likelihood of recurrence
Al-Aly and his team compared the health records of 38,000 persons with two or more proven Covid-19 infections with those of almost 250,000 people who had tested positive for the virus once. As the control group, more than 5.3 million individuals with no history of Covid-19 infection were used.
36,000 individuals had two Covid-19 infections, about 2,200 had it three times, and 246 had it four times among those who experienced reinfections.
Chest pain, irregular heart rhythms, heart attacks, inflammation of the heart muscle or the sac surrounding the heart, heart failure, and blood clots were common new diagnoses following reinfections. According to Al-Aly, common lung conditions included shortness of breath, low blood oxygen levels, lung illness, and fluid buildup around the lungs.
According to the study, the risk of developing a new health issue peaked around the time of Covid-19 reinfection but continued for at least six months. The risk was graded, meaning it rose with each consecutive infection, and it existed whether or not a person had received a vaccination.
Al-Aly claimed that most people don't actually believe that will occur if they receive Covid a second or third time.
The notion that if you've already had Covid, your immune system is taught to recognize it and is better able to fight it, and if you get it again, maybe it doesn't affect you as much, is untrue, according to him.
That doesn't mean there aren't individuals who have had Covid and done perfectly fine, according to Al-Aly; there are plenty of them. Instead, he added, his research demonstrates that each infection carries a new danger, and that risk accumulates over time.
According to him, even if a person only has a 50% chance of experiencing long-lasting health issues during a subsequent infection compared to their initial infection, they would still be 50% more likely to experience issues than someone who did not contract Covid-19 a second time.
The study contains some crucial limitations. According to Al-Aly, reinfections were more frequently observed in those who were already at risk due to their age or underlying condition. Because of this, it is possible that reinfections are not random and neither are the health dangers they pose.
According to Al-Aly, "it's probable that those who are sicker or who have immunological dysfunction are at a higher risk of reinfection and negative health effects after reinfection."
Instead of attempting to isolate the specific effects of reinfection, he was more interested in learning how those who experience repeated illnesses are affected.
"If you get reinfected, does it contribute to your risk of acute problems and long Covid, then the most significant question to people's lives is a clear yes and yes," he said.
Because the study is observational, causation and effect cannot be established.
Al-Aly claims that even after weighing the data to take into consideration the impacts of age, sex, medication use, and the individual's pre-Covid-19 health, the researchers still saw these elevated risks.
Covid-19 keeps surprising us
The research is intriguing, according to experts who weren't involved in it.
"I believe that many people have the mindset that "if I survived my first infection, I should definitely be perfectly fine the second time." Really, there shouldn't be any issues "affirmed Dr. Daniel Griffin, a clinical medicine instructor at Columbia University.
On the podcast "This Week in Virology," Griffin commented on the report, saying, "The general wisdom, right, is that reinfections are modest, nothing to worry about, nothing to see here." But, he claimed, that isn't actually corroborated.
This is not how it should operate. Our immune system typically preserves its memory of how to recognize and fight against some parts of viruses, even when they shape-shift, like influenza does. They might still infect us, but the notion is that our previous immunity will act as some sort of shield and prevent major injury.
The blows keep coming for coronaviruses, particularly SARS-CoV-2 coronaviruses
"You can re-infect yourself with the same coronavirus a year later. Given that coronaviruses have the inherent propensity to affect lifetime immunity, it is unclear whether the second infection can be milder "Griffin stated to CNN.
Griffin claims to have observed Covid-19 reinfections in both directions. For his patients, the second or third dose may be milder, but not always.
Compared to other respiratory infections, how does that compare?
People would contract Covid early in the epidemic, he predicted, and three months would pass before they were largely protected. However, those reinfections are occurring more frequently these days, undoubtedly as a result of the virus's quick alterations. In the last two years, he claims to have seen some individuals infected four times.
Griffin remarked, "We don't really see much of it with the flu."