On Sept. 25, 2024, U.S. 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 published 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).

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).