COVID-19 Vaccine Breakthrough Cases: Data from the States Jennifer Kates, Lindsey Dawson, Emma Anderson, Anna Rouw, Josh Michaud, and Natalie Singer Published: Jul 30, 2021 While COVID-19 vaccines are highly effective at preventing severe disease, hospitalization, and death from COVID-19 and also reduce the likelihood of mild or asymptomatic infection, a small share of fully vaccinated individuals