People vaccinated against Covid-19 in places in the US with high transmission rates have to resume wearing face masks indoors, the Centres for Disease Control and Prevention (CDC) said last week.
This announcement was a major reversal of guidance released in mid-May, which stated that fully vaccinated people weren't required to wear masks in most indoor and outdoor settings. However, with the continued circulation of the highly contagious Delta variant, the US is expecting another surge in Covid-19 cases.
CDC director Rochelle Walensky referenced new data showing that rare breakthrough infections with Delta involve an increased risk of ongoing transmission of the virus. Some vaccinated individuals infected with the Delta variant, she said, "may be contagious and spread the virus to others".