The Centers for Disease Control and Prevention released new data on Friday showing that nearly three quarters of people in Massachusetts who tested positive for COVID-19 were fully vaccinated against the virus.
The data also found that fully vaccinated people who get infected with coronavirus carry as much of it in their nose as unvaccinated people, and can easily spread it to others.
“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 obtained by CNBC. “The masking recommendation was updated to ensure the vaccinated public would not unknowingly transmit virus to others, including their unvaccinated or immunocompromised loved ones.”
This came days after the CDC recommended that fully vaccinated Americans all over the country start wearing masks indoors again. This reversed the course of a prior guidance from the CDC stating that vaccinated people no longer needed to wear masks inside.
Walensky explained earlier in the week that while the delta variant of COVID-19 will hit unvaccinated individuals harder, vaccinated people can carry higher levels of the virus than had been previously thought. She also said that the delta variant acts “uniquely differently from past strains of the virus.”
The CDC then released a document ominously warning that the delta strain of coronavirus is as contagious as the chicken pox and has a longer transmission window than the original strain of COVID-19. It can additionally make older people sicker, even if they have received the vaccine.
The CDC stated that the delta variant of COVID-19 is more transmissible than the common cold, the 1918 Spanish flu, smallpox, Ebola, MERS and SARS.
However, the CDC went on to add that as population-level vaccination coverage increases, vaccinated persons are likely to represent a larger proportion of coronavirus cases across the country. The agency also warned that one limitation in this data is that asymptomatic breakthrough infections might be underrepresented because of detection bias.
Finally, the CDC claimed that these new documents are “insufficient” to draw conclusions about the effectiveness of the authorized vaccines against COVID-19 and the delta variant of it in this outbreak.