Experts show waning effectiveness of COVID-19 vaccines over time

In a letter to The New England Journal of Medicine, publishing online September 1, 2021, an interdisciplinary team of physicians and public health experts at University of California San Diego measured the effectiveness of COVID-19 mRNA vaccines among health workers at UC San Diego Health, most notably during the emergence of the highly transmissible delta virus variant and coincident with the end of the state’s mask mandate, allowing fully vaccinated persons to forgo face coverings in most places.