The CDC got more conservative with its face mask guidelines this week, ahead of unpublished research leaked to the Washington Post. On Friday, that study was released, and the Post calls its findings "sobering." Per the analysis in its weekly Morbidity and Mortality report, the agency notes an "explosive" COVID outbreak in Provincetown, Mass., that kicked off July 4 weekend, driven by the delta variant. Of the 469 people who were infected after traveling to Provincetown from July 3 to July 17—where they packed into indoor and outdoor events at bars, restaurants, and rental homes—nearly 75% of them had been vaxxed. Almost 80% of the vaccinated patients who got COVID had symptoms; of the five patients who ended up hospitalized, four of them had received the vaccine. The research lends credence to the theory that vaccinated people are indeed capable of spreading the virus, including to other vaccinated people, and that viral loads in the vaxxed are similar to those in people who aren't.
"This finding is concerning and was a pivotal discovery leading to [the] CDC's updated mask recommendation," Rochelle Walensky, the agency's director, said in a Friday statement. Despite this data on breakthrough infections, the good news is that the vaccines continue to show great efficacy at keeping most patients from serious illness or death. "If they're lucky—and most people are—they have what looks like a common cold or allergies or sometimes no symptoms at all," Dr. Shira Doron of Tufts Medical Center tells NBC Boston. Amid these developments, Gregg Gonsalves, an associate professor at the Yale School of Public Health, offers further reassurance. "If you're vaccinated, refrain from large group gatherings, and mask up, chances are good you'll be OK," he tells the Post. "This is not 2020." Still, he warns, "we're not out of the woods." Harvard geneticist Pardis Sabeti agrees, noting: "We are at an inflection point. We can either try and take a road to end the pandemic or take a path that will prolong it—a potential nightmare scenario." (Read more coronavirus stories.)