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For many vaccinated Americans, long COVID remains one of the biggest concerns about catching the virus, the fear that even a mild cold could later develop into a lasting, debilitating medical condition. Researchers are now getting a clearer sense of just how likely that is to happen if you're already vaccinated, and so far, the results look promising. NPR's Will Stone reports.
WILL STONE, BYLINE: The vaccines were created to keep you out of the hospital, not to stop long COVID. But Dr. Steven Deeks at the University of California San Francisco says there's been good reason to expect that vaccines would help.
STEVEN DEEKS: Most consequences of an infectious disease is related to the burden of that infection, right? And for COVID, it's the amount of virus that you're infected with.
STONE: And it's clear that if you're vaccinated and then infected, there's going to be less virus in your body than someone who's unvaccinated.
DEEKS: So it would make great sense that the amount of virus-related complications over time would also be lower.
STONE: Sounds simple. Of course, scientists still need to figure out how the virus triggers long COVID in the first place. There are lots of theories, like maybe the infection causes permanent tissue damage or that it injures the blood vessels. Or it could be the virus never leaves the body or provokes an autoimmune response. It's possible all of this could be at play, so for now, the best evidence on how vaccines do against long COVID comes from a growing number of real-world studies. Here's Deeks again.
DEEKS: In general, if you look across all the various different papers in this area, the consensus is that if you are vaccinated and become infected, your risk of developing long COVID is reduced.
STONE: Just how much is hard to say. Deeks puts it roughly around 50%. But the problem is it can be hard to compare studies, in part because they have different definitions of long COVID - which symptoms count, how many and how long they need to last. Michael Edelstein is an epidemiologist at Bar-Ilan University in Israel. His study followed several thousand people.
MICHAEL EDELSTEIN: For those who were infected, approximately 4 to 10 months after their infection, we checked whether they were still experiencing symptoms.
STONE: They found a big difference. The fully vaccinated were 50 to 80% less likely to report most of the common symptoms - like fatigue, headache, shortness of breath - compared to the unvaccinated.
EDELSTEIN: I think the evidence from this study, similar to other studies that are roughly coming out at the same time, I think, shows a pretty profound protective effect.
STONE: Another study took a different approach, analyzing thousands of electronic health records from the VA. Dr. Ziyad Al-Aly of the St. Louis VA says they measured a range of medical problems at six months after infection.
ZIYAD AL-ALY: The risk of long COVID is slightly lower than people who had COVID-19 without vaccination, but it doesn't really go away totally.
STONE: He says being vaccinated seemed to make the biggest difference in two specific ways.
AL-ALY: People are having less shortness of breath and less cough, less lingering manifestations in the lungs and then, two, less blood clotting.
STONE: And he says the lower risk of long COVID was true even for vaccinated people who were so sick they ended up in the hospital. But David Putrino at Mount Sinai in New York City cautions vaccination is not going to completely protect you. He cares for plenty of long COVID patients who got sick when they were vaccinated.
DAVID PUTRINO: I don't think in good faith I would be able to distinguish between someone who has a breakthrough case of long COVID versus a pre-vaccine case of long COVID. The symptoms are very consistent.
STONE: And now the big question is, what will the aftermath of omicron look like? Scientists don't yet have good data on that variant and long COVID, but Putrino plans to play it safe. He says the best way to avoid long COVID is not to get infected in the first place. Will Stone, NPR News. Transcript provided by NPR, Copyright NPR.