COVID-19 vaccines significantly reduce the likelihood of hospital workers testing positive for a coronavirus infection, two studies published in the JAMA Network suggest.
Both studies were published May 6.
In the first study, researchers from St. Jude Children's Research Hospital in Memphis, Tenn., analyzed data for vaccinated and unvaccinated workers at the hospital. A total of 3,052 hospital employees had received at least one Pfizer-BioNTech vaccine dose between Dec. 17, 2020, and March 20, 2021. More than 2,775 had received two doses during that time, and 2,165 were unvaccinated.
During the study period, 51 of the vaccinated workers tested positive for coronavirus during follow-up (41 before and 10 after the second dose), and 29 were diagnosed but asymptomatic, according to the study.
Researchers said 185 of the unvaccinated workers contracted coronavirus, and 79 of them did not have symptoms.
Median follow-up was 81 days among unvaccinated employees, and 72 days, on average, among vaccinated employees.
Overall, researchers said vaccination was associated with a decreased risk of symptomatic and asymptomatic infections. They did not find any symptomatic or known exposure cases more than seven days after the second shot during that time.
In the second study, researchers examined data for 6,710 healthcare workers at Tel Aviv Sourasky Medical Center in Israel. A total of 5,953 healthcare workers received at least one dose of the Pfizer-BioNTech vaccine between Dec. 20, 2020, and Feb. 25, 2021. More than 5,515 received two doses, and 757 were unvaccinated.
Researchers said eight fully vaccinated workers (more than seven days after receipt of the second shot) contracted a symptomatic coronavirus infection, compared to 38 unvaccinated workers. Nineteen fully vaccinated workers and 17 unvaccinated workers were diagnosed but asymptomatic, according to the study.
The researchers concluded in this study also that vaccination was associated with significantly lower risk of infection.
Read more about the first study and its limitations here. Read more about the second study and its limitations here.