AdvertisementHow A Gay Community Helped The CDC Spot A COVID Outbreak — And Learn More About Delta05:31Download AudioResumeAugust 06, 2021Selena Simmons-DuffinfacebookEmailA data scientist working in tech, Michael Donnelly became an amateur COVID-19 watcher early in the pandemic. When his vaccinated friends started getting sick following July Fourth festivities in Provincetown, Mass., he documented more than 50 breakthrough cases that ultimately led the CDC to changing its guidance on masking. (Jason LeCras for NPR)