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Study: Vaccinated people can carry as much virus as others

  • In this May 21 file photo, a person holds a mask while walking outside in Philadelphia. (AP Photo/Matt Rourke, File)

In another dispiriting setback for the nation’s efforts to stamp out the coronavirus, scientists who studied a big COVID-19 outbreak in Massachusetts concluded that vaccinated people who got so-called breakthrough infections carried about the same amount of the coronavirus as those who did not get the shots.

Health officials on Friday released details of that research, which was key in this week’s decision by the Centers for Disease Control and Prevention to recommend that vaccinated people return to wearing masks indoors in parts of the U.S. where the delta variant is fueling infection surges. The authors said the findings suggest that the CDC’s mask guidance should be expanded to include the entire country, even outside of hot spots.

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The findings have the potential to upend past thinking about how the disease is spread. Previously, vaccinated people who got infected were thought to have low levels of virus and to be unlikely to pass it to others. But the new data shows that is not the case with the delta variant.

The outbreak in Provincetown — a seaside tourist spot on Cape Cod in the county with Massachusetts’ highest vaccination rate — has so far included more than 900 cases. About three-quarters of them were people who were fully vaccinated.

Travis Dagenais, who was among the many vaccinated people infected, said “throwing caution to the wind” and partying in crowds for long nights over the July Fourth holiday was a mistake in hindsight.

“The dominant public messaging has been that the vaccine means a return to normal,” the 35-year-old Boston resident said Thursday. “Unfortunately, I’ve now learned it’s a few steps toward normal, not the zero-to-sixty that we seem to have undertaken.”

Dagenais credits being vaccinated with easing the worst of the flu-like symptoms in a couple of days. He has recovered.

Like many states, Massachusetts lifted all COVID-19 restrictions in late May, ahead of the traditional Memorial Day start of the summer season. Provincetown this week reinstated an indoor mask requirement for everyone.

Leaked internal documents on breakthrough infections and the delta variant suggest the CDC may be considering other changes in advice on how the nation fights the coronavirus, such as recommending masks for everyone and requiring vaccines for doctors and other health workers.

The delta variant, first detected in India, causes infections that are more contagious than the common cold, flu, smallpox and the Ebola virus, and it is as infectious as chickenpox, according to the documents, which mentioned the Provincetown cases.

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The documents were obtained by The Washington Post. As they note, COVID-19 vaccines are still highly effective against the delta variant at preventing serious illness and death.

The Provincetown outbreak and the documents highlight the enormous challenge the CDC faces in encouraging vaccination while acknowledging that breakthrough cases can occur and can be contagious but are uncommon.