CDC drops mask guidance for the vaccinated, then reinstates it for Delta

CDC Director Rochelle Walensky announced May 13 that fully vaccinated people could forgo masks indoors and outdoors in most settings — a sudden shift that surprised even some administration allies. On July 27, CDC reversed for areas of substantial/high transmission, citing Delta-variant data showing vaccinated people could transmit. The sequence became the most-cited example of COVID-era guidance whiplash — read by critics as political rather than steady science, and by defenders as guidance tracking evolving evidence.