The following is a summary of “Pfizer-BioNTech Coronavirus Disease 2019 Vaccine Effectiveness Against Severe Acute Respiratory Syndrome Coronavirus 2 Infection Among Long-term Care Facility Staff With and Without Prior Infection in New York City, January–June 2021,” published in the February 2023 issue of Infectious Diseases by Peebles, et al.
For a study, researchers sought to assess the effectiveness of the Pfizer-BioNTech COVID-19 vaccine in reducing the risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in long-term care facility staff in New York City aged under 65 years.
The study evaluated the impact of prior infection without vaccination, vaccination without prior infection, and vaccination after prior infection compared to unvaccinated people without prior infection. The research involved weekly SARS-CoV-2 testing from January 21 to June 5, 2021, of long-term care facility staff in New York City aged <65 years, and test results were obtained from state-mandated laboratory reporting. Vaccination status was acquired from the Citywide Immunization Registry, and Cox proportional hazards models were employed to adjust for confounding with inverse probability of treatment weights.
The study findings indicated that the risk of incident SARS-CoV-2 infection was significantly lower in all groups compared to unvaccinated people without prior infection. Unvaccinated people with prior infection had a 54.6% (95% CI: 38.0%–66.8%) lower risk of infection. Fully vaccinated people without prior infection had an 80.0% (67.6%–87.7%) lower risk of infection, and those who were fully vaccinated after prior infection had an 82.4% (70.8%–89.3%) lower risk of infection.
These results demonstrated that two doses of the Pfizer-BioNTech COVID-19 vaccine reduced the risk of SARS-CoV-2 infection by at least 80%, and increased protection from prior infection alone. Therefore, the findings supported the recommendation that all eligible individuals should be vaccinated against COVID-19, regardless of their prior infection history.