Outbreak of SARS-CoV-2 infections, including COVID-19 vaccine breakthrough infections

… vaccination coverage among eligible Massachusetts residents was 69%

… three quarters (346; 74%) of cases occurred in fully vaccinated persons

… 274 (79%) vaccinated patients with breakthrough infection were symptomatic

… Among five COVID-19 patients who were hospitalized, four were fully vaccinated

… even jurisdictions without substantial or high COVID-19 transmission

… masking in indoor public settings regardless of vaccination status

… Further investigations and characterization of breakthrough infections and vaccine effectiveness among this highly vaccinated population are ongoing