It found that people who had received even one dose of a Covid vaccine before their infection were seven to 10 times less likely to report two or more symptoms of long Covid 12 to 20 weeks later. The study, which was led by Michael Simon, Arcadia’s director of data science, and Dr. Richard Parker, the firm’s chief medical officer, also found that people who received their first vaccine dose after contracting the coronavirus were less likely to develop long Covid than those who remained unvaccinated, and the sooner they were vaccinated after infection, the lower the risk of long-term symptoms.
But results from another study, also not yet peer-reviewed, were more discouraging about the ability of vaccines to prevent long Covid. The study was conducted by researchers in the United Kingdom who analyzed electronic medical records of patients in the United States. It compared about 10,000 people who had received Covid vaccines with a similar number of people who had not been vaccinated against the coronavirus but did have a flu vaccine — an effort to limit the number of people in the study who might be considered vaccine hesitant or who generally had less healthy behaviors, the researcher said.
The study found that having a coronavirus vaccine before being infected did not reduce the risk of most symptoms of long Covid. There was some suggestion from the data that vaccinated people might be at lower risk of long-term issues like abnormal breathing and cognitive symptoms, the authors wrote, but those results were not statistically conclusive.
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The authors said it was possible that because their data relied on electronic health records, the study might have captured only patients with the most severe symptoms, rather than a wider range of patients who did not seek medical attention for their symptoms.
Can vaccines help if you already have long Covid?
When vaccines were first rolled out, before the emergence of the more contagious Delta variant which preceded the even-more-contagious Omicron variant, some patients with long Covid were finding that symptoms like brain fog, joint pain, shortness of breath and fatigue improved after they were vaccinated. Still, many people experienced no difference in their symptoms after vaccination and a small percentage said they felt worse.
A study by the Office for National Statistics in the United Kingdom found that in people ages 18 to 69 who reported their symptoms between February and September 2021, a first dose of a vaccine lowered the odds of reporting long Covid symptoms by 13 percent. A second dose further lowered the odds by 9 percent, the study found.