Study shows dramatic decline in effectiveness of all three COVID-19 vaccines over time

As the Delta variant became the dominant strain of coronavirus across the United States, all three COVID-19 vaccines available to Americans lost some of their protective power, with vaccine efficacy among a large group of veterans dropping between 35% and 85%, according to a new study.

Researchers who scoured the records of nearly 800,000 U.S. veterans found that in early March, just as the Delta variant was gaining a toehold across American communities, the three vaccines were roughly equal in their ability to prevent infections.