CDC shares 'pivotal discovery' on COVID-19 breakthrough infections that led to new mask guidance
CAPE COD, Mass. -- A new study shows the delta COVID-19 variant produced similar amounts of virus in vaccinated and unvaccinated people if they get infected -- illustrating a key motivation behind the federal guidance that now recommends most fully vaccinated Americans wear masks indoors.
Experts say that vaccination makes it less likely that you'll catch COVID-19 in the first place -- but for those who do, this data suggests they could have a similar tendency to spread it as unvaccinated folks.
"High viral loads suggest an increased risk of transmission and raised concern that, unlike with other variants, vaccinated people infected with delta can transmit the virus," Dr. Rochelle Walensky, director of the US Centers for Disease Control and Prevention, said in a statement Friday.
The study, published by CDC Friday, describes 469 Massachusetts residents who were infected in a July outbreak in Barnstable County, which includes the summer vacation destination Provincetown. No deaths were reported among them.
About 74% -- or 346 cases -- had been fully vaccinated. Of those cases, 79% reported symptoms. Genetically sequenced cases revealed the delta variant as the main culprit.
