evidence: - The data reported from these states indicate that breakthrough cases, hospitalizations, and deaths are extremely rare events among those who are fully vaccinated against COVID-19 (see Figure 1). The rate of breakthrough cases reported among those fully vaccinated is below 1% in all reporting states, ranging from 0.01% in Connecticut to 0.54% in Arkansas. [...] - The rates of death among fully vaccinated people with COVID-19 were even lower, effectively zero (0.00%) in all but two reporting states, Arkansas and Michigan where they were 0.01%. (Note: Deaths may or may not have been due to COVID-19.) [...] While information on breakthrough events is still limited and incomplete, this analysis of available state-level data indicates that COVID-19 breakthrough cases, and especially hospitalizations and deaths, among those who are fully vaccinated are rare occurrences in the United States. Moreover, this data indicate the vast majority of reported COVID-19 cases, hospitalizations, and deaths in U.S. are among those who are unvaccinated or not fully vaccinated. These findings echo the abundance of data demonstrating the effectiveness of currently authorized COVID-19 vaccines. Moving forward, particularly as the more transmissible Delta variant is now the dominant strain of COVID-19 circulating in the U.S., more robust state-level data will help to monitor ongoing vaccine effectiveness and inform discussions about booster vaccinations.