As the more contagious Delta variant of COVID-19 surges in parts of the United States, a new study from Yale University and the Commonwealth Fund finds that the U.S. vaccination campaign has significantly curbed the virus’s death toll, saving as many as 279,000 lives and averting up to 1.25 million hospitalizations. The study examined the impact of the U.S. COVID-19 vaccination program on the pandemic’s trajectory through July 1, 2021, considering the emergence of more transmissible variants in recent months. The findings demonstrate that the speed of the U.S. vaccination rollout prevented numerous additional COVID-19 fatalities and hospitalizations. Researchers warn, however, that the Delta variant’s spread among unvaccinated populations could produce a surge in new cases and reverse the downward trend of infections and deaths across the country.