A new study of the US Centers for Disease Control and Prevention (USCDC) shows the Delta variant produced similar amounts of virus in vaccinated and unvaccinated people if they get infected. The study details a COVID-19 outbreak that started July 3 in Provincetown, Mass., involving 469 cases. It found that three-quarters of cases occurred in fully vaccinated people. Massachusetts has a high rate of vaccination: about 69% among eligible adults in the state at the time of the study.
The study, published by the CDC on Friday, focused on 469 Covid-19 cases identified among Massachusetts residents who had travelled to Barnstable County, a summer vacation destination, during July 3 to 17, A total of 346 cases, about 74 per cent, occurred in fully vaccinated people, according to the study. Testing identified the Delta variant in 90 per cent of specimens from 133 patients.
The study demonstrated that Delta infection resulted in similarly high SARS-CoV-2 viral loads in vaccinated and unvaccinated people, said CDC Director Rochelle Walensky. The CDC suggested jurisdictions to consider expanded prevention strategies, including universal masking in indoor public settings, particularly for large public gatherings that include travellers from many areas with differing levels of SARS-CoV-2 transmission.