Breakthrough COVID infections in fully vaccinated people aren't so rare, CDC says

A report released Friday by the Centers for Disease Control and Prevention confirms that fully vaccinated people are getting breakthrough infections of COVID-19 caused by the delta variant, and if they do get it, they might be as likely to spread it as unvaccinated people.

The CDC report shows data from clusters of an outbreak in Barnstable County, Massachusetts, where 74% of the 469 identified COVID cases were in fully vaccinated people. Ninety percent of the cases tested were caused by the delta variant. Vaccinated people who had COVID had about as much virus in their nose as unvaccinated people who were infected, according to the report.

Four fully vaccinated people were hospitalized in the cases studied, and no deaths were reported. This syncs up with previous research that shows the vaccines are effective at preventing severe disease and death from the coronavirus, even delta.

The analysis comes days after the CDC recommended fully vaccinated people go back to wearing masks indoors if they live in an area with substantial or high rates of COVID-19, citing research that shows just how contagious the now-dominant delta variant is. After its recommendation, the agency was criticized by some scientists and members of the media for failing to cite its research or show its sources. 

On Thursday, the Washington Post published an internal presentation from the CDC, which confirmed that delta is much more contagious than previous variants of the coronavirus (more transmissible than the common cold or flu, and about as contagious as chicken pox) and most likely leads to more severe disease. The presentation also raises the question of how public officials can relay information to the public that -- even though delta is more contagious and leads to more breakthrough infections in vaccinated people -- the vaccines are still working.