US healthcare workers receiving additional vaccine doses during the Omicron period (December 2021 to April 2022) had a 45% lower risk of having symptoms 6 weeks after COVID-19 infection, according to a study today in Open Forum Infectious Diseases. 

The study results came from self-reported symptom questionnaires completed 6 weeks after the onset of symptoms, and was a sub-analysis of data collected during the Preventing Emerging Infections through Vaccine Effectiveness Testing Project (Project PREVENT).

In total, the researchers enrolled 2,478 participants, of whom 1,422 (57%) had COVID-19. All participants were fully vaccinated with two doses of COVID-19 vaccine, and 66.3% had received a third, booster dose. All participants reported COVID-19–like symptoms within 14 days of a qualifying test. 

The prevalence of symptoms at 6 weeks was 26% (373) in those with COVID-19 and 18% (195) in those without COVID-19. SARS-CoV-2–positive participants had either fever or cough as an initial symptom in 71.9% of cases.

Lower odds of symptoms with recent booster 

Among participants who had COVID-19, those who had received an additional COVID-19 vaccine dose had a lower prevalence of any symptoms than those who had not at 6 weeks post-infection (adjusted odds ratio [aOR], 0.55; 95% confidence interval [CI], 0.43 to 0.70). 

If the third vaccine dose was administered 16 weeks or less before infection, healthcare providers had lower odds of reporting respiratory symptoms (aOR, 0.69; 95% CI, 0.46 to 0.99), psychiatric symptoms (aOR, 0.68; 95% CI, 0.47 to 0.99), or any symptom (aOR, 0.68; 95% CI, 0.53 to 0.87) than those who received the dose more than 16 weeks earlier. 

COVID-19 vaccination might lead to fewer 6-week symptoms among persons with symptomatic infection because of its effect in attenuating the severity of acute illness.

"COVID-19 vaccination might lead to fewer 6-week symptoms among persons with symptomatic infection because of its effect in attenuating the severity of acute illness," the authors concluded.

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