Vaccinated people are less likely to get so-called long COVID, while those infected while unvaccinated may recover from persistent symptoms faster if they get the shot, a U.K. Health Security Agency review determined.
Fully vaccinated people who became infected with COVID-19 were roughly half as likely to have any symptoms lasting more than a month, 78% less likely to have symptoms lasting 12 to 20 weeks, and 13% less likely to have at least one symptom at 6 months, according to six of the eight studies summarized in a rapid evidence briefing document.
One preprint study of moderate quality suggested the opposite -- a more than twofold higher risk of symptoms at 4 weeks from the date of diagnosis versus unvaccinated participants -- but it wasn't clear why this study contradicted the rest, the document noted, calling for more analysis.
In studies that broke down symptoms individually, there was lower likelihood of developing olfactory dysfunction and significantly lower risk at 6 months for anosmia, fatigue, hair loss, interstitial lung disease, myalgia, and "other" pain.
These findings are likely an underestimate of the effectiveness of vaccination in preventing long COVID, since the studies included only vaccinated people who were infected, not those who had infection prevented entirely, the document pointed out.
The review also found that people who already had long COVID but then got vaccinated were more likely to have improvement in symptoms -- either immediately or in the weeks afterward -- compared with those who remained unvaccinated, although most had no change in symptoms and a small number had worsening after vaccination.
The one study that looked at timing of vaccination suggested that getting the shot sooner was much better than later in terms of likelihood of symptom improvement.
"These studies add to the potential benefits of receiving a full course of the COVID-19 vaccination," said Mary Ramsay, MBBS, head of immunization at the U.K. agency, in a statement. "Vaccination is the best way to protect y