COVID-19 mRNA vaccines highly effective in large real-world study of health care workers
The effectiveness of the COVID-19 messenger RNA vaccines exceeded 96% among a cohort of more than 49,000 health care workers, according to a study published in Clinical Infectious Diseases.
“In our health care worker population, under real-world settings where everything might not be as controlled as a clinical trial, these vaccines worked really well, despite some incursion of variant strains in our states,” Melanie Swift, MD, MPH, an occupational medicine specialist in the division of preventive, occupational and aerospace medicine at Mayo Clinic, told Healio. “Clinicians should be very confident in the effectiveness of these vaccines and should strongly recommend vaccination to vaccine-hesitant patients.”
Swift and colleagues conducted a retrospective review of health care workers (HCWs) who were newly diagnosed with COVID-19 between Jan. 1 and March 3. They examined 2-week COVID-19 incidence rates in this population and reviewed data from 45,162 HCWs who received two doses of an mRNA vaccine and 4,058 who received a single dose.
A total of 1,125 participants tested positive for SARS-CoV-2, for an average 2-week incident rate of 26.4 per 10,000 population. According to Swift and colleagues, 964 of newly infected HCWs were symptomatic at the time of analysis, 143 were asymptomatic and 18 could not be assessed.
They calculated the effectiveness of the Pfizer-BioNTech vaccine to be around 78% after one dose and approximately 97% after two doses. The Moderna vaccine was calculated to be around 91% effective after one dose and almost 99% effective after two doses.
“Many people were waiting to see if they would be safe and if they would really work. I think the answer on both counts is now a definitive yes,” Swift said.
Swift said the study’s observational design did not allow the researchers to control for personal factors that may affect a person’s willingness to be vaccinated, and that confounding may have occurred because people who took the vaccine likely observed other recommended COVID-19 precautions.
“If we adopt a mandatory vaccination policy down the road, that would remove this confounder and we can repeat the analysis to see if the outcomes are the same when applied to people who didn’t necessarily want to be vaccinated,” Swift said.