CDC shares "pivotal discovery" on Covid-19 breakthrough infections

 

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 again.   The study, published by the US Centers for Disease Control last week, 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.   The researchers found evidence that viral loads were similar among 127 fully vaccinated people and 84 others who were unvaccinated, partially vaccinated or whose vaccination status was unknown. Viral load is a proxy for how likely someone might be to transmit the virus to others.   “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,” CDC Director Dr. Rochelle Walensky said in a statement.