COVID-19 Vaccine Effectiveness Down Against New Infections in New York

Currently available vaccines are effective for preventing severe acute respiratory syndrome coronavirus-2 infection and COVID-19-associated hospitalization, but vaccine effectiveness has declined in recent months in New York, according to research published in the Aug. 18 early-release issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.

Eli S. Rosenberg, Ph.D., from the New York State Department of Health in Albany, and colleagues linked statewide immunization, laboratory testing, and hospitalization databases for New York to estimate the rates of new laboratory-confirmed COVID-19 cases and hospitalizations by vaccination status among adults having received one of the three vaccines the U.S. Food and Drug Administration has authorized for emergency use.

The researchers found that the overall age-adjusted vaccine effectiveness against new COVID-19 cases for all adults decreased from 91.9 to 79.8 percent during May 3 to July 25, 2021. The overall age-adjusted vaccine effectiveness against hospitalization was relatively stable during the same period, ranging from 91.9 to 95.3 percent.

"Vaccine effectiveness against infection appears to have declined in recent months in New York, coinciding with a period of easing societal public health restrictions and increasing delta variant circulation," the authors write. "These findings support a multipronged approach to reducing new COVID-19 hospitalizations and cases, centered on vaccination, and including other approaches such as masking and physical distancing."