A meta-analysis of six studies estimates that one dose or more of COVID-19 vaccine is 29% effective against symptoms persisting for at least 3 weeks after infection, or long COVID.
In the study, published today in Antimicrobial Stewardship & Healthcare Epidemiology, a team led by University of Iowa researchers analyzed data from six observational studies on vaccine effectiveness (VE) against long COVID published from Dec 1, 2019, to Apr 27, 2022. The studies were from Israel, Italy, the United Kingdom, and the United States.
The 251,123 total participants had received at least one dose of Pfizer/BioNTech, Moderna, AstraZeneca, or Johnson & Johnson vaccine. Among unvaccinated participants, the pooled prevalence of long COVID was 39.1%, compared with 37.6% among vaccine recipients.
The pooled diagnostic odds ratio (DOR) for long COVID was 0.708, with an estimated VE of 29.2% (95% CI, 27.5% to 30.8%). The DOR was 0.647, and VE was 35.3% (95% CI, 32.3% to 38.1%) among those vaccinated only before contracting COVID-19 (four studies). Among those vaccinated only after infection (three studies), the DOR was 0.726, and VE was 27.4% (95% CI, 25.4% to 29.3%).
The most common symptoms were fatigue or muscle weakness, muscle pain, anxiety, impaired memory, sleep difficulties, and shortness of breath.
The authors said the results suggest that COVID-19 vaccines are more effective against persistent symptoms when given before infection, although recipients of post-infection doses also had some protection.
"COVID-19 vaccination both before and after having COVID-19 significantly decreased post–COVID-19 conditions for the circulating variants during the study period although vaccine effectiveness was low," they wrote. "Our findings can reassure that individuals with prolonged COVID-19 symptoms who have not been vaccinated that they should do so."
The researchers called for more observational studies on other types of COVID-19 vaccines (eg, inactivated virus), vaccination after infection, VE of a booster dose and of mixed COVID-19 vaccines, and genomic surveillance. "A more standardized definition of post–COVID-19 conditions is also needed both for research and clinical purposes," they concluded.