Impact of Vaccination on the COVID-19 Pandemic: Evidence from U.S. States

Abstract

Governments worldwide are implementing mass vaccination programs in an effort to end the novel coronavirus (COVID-19) pandemic. Here, we evaluated the effectiveness of the COVID-19 vaccination program and predicted the path to herd immunity in the U.S. We estimated that vaccination reduced the total number of new cases by 4.4 million (from 33.0 to 28.6 million), prevented approximately 0.12 million hospitalizations (from 0.89 to 0.78 million), and decreased the population infection rate by 1.34 percentage points (from 10.10–8.76%). We built a Susceptible-Infected-Recovered (SIR) model with vaccination to predict herd immunity. Our model predicts that the U.S. can achieve herd immunity by the last week of July 2021, with a cumulative vaccination coverage of 60.2%. Herd immunity could be achieved earlier with a faster vaccination pace, lower vaccine hesitancy, and higher vaccine effectiveness. These findings improve our understanding of the COVID-19 vaccination and can inform future public health policies.