About three-fourths of people infected in a Massachusetts Covid-19 outbreak were fully vaccinated against the coronavirus with four of them ending up in the hospital, according to new data published Friday by the Centers for Disease Control and Prevention.
The new data, published in the U.S. agency’s Morbidity and Mortality Weekly Report, also found that fully vaccinated people who get infected carry as much of the virus in their nose as unvaccinated people, and could spread it to other individuals.
“This finding is concerning and was a pivotal discovery leading to CDC’s updated mask recommendation,” CDC Director Dr. Rochelle Walensky said in a statement. “The masking recommendation was updated to ensure the vaccinated public would not unknowingly transmit virus to others, including their unvaccinated or immunocompromised loved ones.”
On Tuesday, the CDC reversed course on its prior guidance and recommended fully vaccinated Americans who live in areas with high Covid infection rates resume wearing face masks indoors. The guidelines cover about two-thirds of the U.S. population, according to a CNBC analysis.
A CDC document that was reviewed by CNBC warned that the delta variant sweeping across the country is as contagious as chickenpox, has a longer transmission window than the original Covid strain and may make older people sicker, even if they’ve been fully vaccinated.
Delta, now in at least 132 countries and already the dominant form of the disease in the United States, is more transmissible than the common cold, the 1918 Spanish flu, smallpox, Ebola, MERS and SARS, according to the document. Only measles appears to spread faster than the variant.