Evidence Grows That Vaccines Lower The Risk

The chance of even a mild case of COVID-19 turning into a long-term, debilitating medical condition is one of the greatest fears of Americans trying to navigate the pandemic, which is again taking a turn as new data show the BA.2 subvariant is taking hold in the U.S.

Unfortunately, the only sure way to avoid long COVID is not to catch the virus in the first place.

But there is now a growing body of research that’s offering at least some reassurance for those who do end up getting infected — being fully vaccinated seems to substantially cut the risk of later developing the persistent symptoms that characterize long COVID.

While many of the findings are still preliminary, the handful of studies that have emerged in the past half year are telling a relatively consistent story.

“It may not eradicate the symptoms of long COVID, but the protective effect seems to be very strong,” says epidemiology professor Michael Edelstein, of Bar-Ilan University in Israel, who’s studying long COVID.

Edelstein’s study was one of those included in a recent analysis of the evidence on long COVID and vaccination done by the UK Health Security Agency. That review found vaccinated people tend to have lower rates of long COVID after an infection than those who are unvaccinated.

There’s a running list of theories about why people get long COVID. Permanent tissue damage from the infection, injury to blood vessels and the development of microclots, a lingering viral reservoir in parts of the body, or an autoimmune condition are some of the ideas being explored in the research.

But even without a clear sense of what’s exactly driving long COVID, there’s good reason to believe that vaccines would help guard against the condition, says Dr. Steven Deeks, a professor of medicine at the University of California, San Francisco.

There’s overwhelming evidence that someone who’s vaccinated has less virus in their body during an infection, he says, “so it would make great sense that the amount of virus-related complications over time would also be lower.”

Looks good… but how good?

One of the ongoing challenges with long COVID research is simply defining the condition — with each study taking slightly different approaches as to what symptoms count and how long they need to last after the initial infection.

This inconsistency makes it hard to pull together a single estimate for how much vaccines limit long COVID.

Generally, though, Deeks says vaccinated people seem to have a 50% lower average risk of developing long COVID than unvaccinated people. This is in the range of what multiple studies in the U.K., Israel and the U.S. have found.

Ideally, long COVID should not be measured only a few months after the initial infection, he says. “A lot of people are still slowly getting better, so you have to wait at least four months to sort of figure out whether or not these symptoms will persist.”

The Israeli study, conducted by Edelstein and his colleagues, followed several thousand people who were unvaccinated, partially vaccinated and fully vaccinated. Those who tested positive were asked to self-report their symptoms between four and eight months after their initial infection.

Participants who had two or three doses of the vaccines were about 50% to 80% less likely to report seven of the 10 most common symptoms, which include shortness of breath, headache, weakness and muscle pain.

Edelstein says these results are not necessarily surprising, because they’re compatible with other recent studies. “It gives us a little bit of reassurance that if you’re vaccinated, you reduce your chances of long COVID quite substantially.”

Indeed, some researchers have found similar results by combing through electronic records from health care providers in the U.S. That massive study concluded that patients who had at least one vaccine dose were seven to 10 times less likely to report two or more long COVID symptoms compared to unvaccinated people between 12 and 20 weeks after their infection.

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