These risks, which were present regardless of vaccination status, persisted even six months after reinfection, at which point they entered long COVID territory. The median amount of time between a first and second infection was about two and a half months, and about two months passed between the second and third infection. (The results were adjusted for demographic and health characteristics.)
Put simply, “getting hit with a baseball bat once is better than getting hit five times,” said Al-Aly, who is the lead author of the study. This phenomenon is also common following reinfections with Dengue fever, a mosquito-borne illness that occurs in tropical regions, Al-Aly told BuzzFeed News, in which any subsequent infection increases the risks of developing severe sickness.
It’s an idea called the “multiple hit hypothesis,” according to Erin Sanders, a clinical scientist studying long COVID and Lyme disease at MIT. “For a number of environmental exposures, genetic predispositions, and stressors that you encounter, it may lead to somebody being more prone to infection or severe illness and that’s something that I very much think is going to be at play with all of this.”
Not all experts think reinfections can cause cumulative damage
Dr. Shira Doron, an infectious disease physician and hospital epidemiologist at Tufts Medical Center, recommended that people take Al-Aly’s findings with a grain of salt. Because the study only included veterans, who tend to have more underlying health problems than the general public, Doron doubts the results are generalizable to everyone else.
“We know that over any period of time, and certainly over the period between one infection and another, chronic underlying conditions can get worse. That’s the natural course,” Doron said. “I don’t want people to think that the norm is to have chronic disease as a result of the first infection and then worsening chronic disease as a result of each next one.”
Some of Doron’s skepticism is based on research that shows adults and children experience similar or less severe symptoms during their second COVID infection compared with their first, and that the risk of reinfection decreases over time.
Gerardo Chowell, an epidemiology and biostatistics professor at the Georgia State University School of Public Health, isn’t surprised that coronavirus reinfections may cause mounting damage to your body, although he said this may not be true for everyone. Even before the pandemic, Chowell said, Americans’ overall baseline health had been declining, which can make people more vulnerable to infections of all kinds.
“People with weakened immune systems will have a harder time recovering from the virus, and that’s the most significant issue here,” said Chowell, adding that he’s hopeful SARS-CoV-2 will eventually become milder. (Evolutionarily speaking, viruses don’t benefit from killing people — doing so ruins their chance of surviving and spreading in the population.)
“This doesn’t mean it won’t be able to kill people, it definitely will, but perhaps not on the level that we saw during the first two years of circulation,” Chowell said.
How could repeat infections affect the body?
How and why repeat exposures might affect the body remains largely unknown. The theories that do exist mirror those for long COVID.
One explanation is that an initial infection may cause serious injury somewhere in the body that may be unnoticeable at first until a subsequent infection “pushes them over the edge,” Al-Aly said. This may be especially true for people who may not know they have a medical condition like kidney damage or a heart problem.
Another possibility is that coronavirus particles are able to remain hidden in different parts of the body like the brain, gut, eyes, and heart, silently causing damage that accumulates with each infection. There’s also the theory that COVID triggers an autoimmune response that kicks a person’s immune system into overdrive, bringing about widespread inflammation that can cause symptoms like fatigue, brain fog, muscle aches, and more.
The problem, Doron of Tufts said, is that many of these speculations have little scientific backing. “All of the things that have been on the list as potential causes haven’t reliably been found in all of the people that have been studied and so it just makes it really, really hard to know.”
Can vaccination reduce the risks from reinfections?
There is at least some indication that vaccination can lower the risk of developing post-COVID symptoms. A review of 15 studies found that people who received two doses of a COVID vaccine were about half as likely to develop long COVID symptoms that persisted for over a month; this effect was stronger in those older than 60 and lowest among 19- to 35-year-olds. The findings are promising given nearly 1 in 5 adults in the US who have had COVID are experiencing long COVID, according to the CDC.
How someone responds to COVID or vaccination depends on a myriad of factors, including their health status and general lifestyle habits, as well as the circulating variant at the time and the societal preventive measures in places like mask requirements.
For now, the best way to avoid poor outcomes following each infection is to avoid infection altogether, get vaccinated, and seek treatment like Paxlovid as early into your bout with the virus as possible, if eligible.
“Every time you get infected, you’re rolling the dice for a good or bad outcome. So as you continue to play that game, you again increase your risks,” Sanders of MIT said. “One of the biggest things that anyone can do right now is to protect yourself from getting infected again, and even if you aren’t able to fully prevent infection, there’s something to be said for reducing the amount of virus and the dose of virus that you’re exposed to.” ●