CDC study shows three-fourths of people infected in Massachusetts coronavirus outbreak were vaccinated but few required hospitalization

A sobering scientific analysis published Friday found that three-quarters of the people infected during an explosive coronavirus outbreak fueled by the delta variant were fully vaccinated. The report on the Massachusetts cases, from the Centers for Disease Control and Prevention, offers key evidence bolstering the hypothesis that vaccinated people can spread the more transmissible variant and may be a factor in the summer surge of infections.

The data, detailed in the CDC’s Morbidity and Mortality Weekly Report, helped persuade agency scientists to reverse recommendations on mask-wearing and advise that vaccinated individuals wear masks in indoor public settings in some circumstances.

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