Just two months after lifting the COVID-19 mask mandate, the CDC is now recommending that some vaccinated people should resume wearing masks indoors in areas with high or substantial transmission of COVID-19.

CDC director Dr. Rochelle Walensky made the announcement Tuesday as nationwide concern over the delta variant of COVID-19 grows and cases increase.

Last week, a CDC spokesman said the agency had no plans to alter its guidance unless there were a significant change in the science. On Tuesday, CNN reported that federal officials met over the weekend to review new evidence that may have prompted the reversal.

This news comes as COVID-19 cases are rising across the country due to the delta variant. While there are breakthrough cases of the virus in people who were fully vaccinated, “over 99% of the COVID-19 cases, hospitalizations and deaths we are seeing are among unvaccinated individuals,” according to L.A. County Public Health Director Barbara Ferrer.

Despite the vaccines proving effective against the virus and its variants, some medical experts believe the CDC’s recommendation is a “move in the right direction.”

This month, several Hollywood events began requiring negative COVID-19 tests, even from fully vaccinated individuals. The Cannes Film Festival, which wrapped up last Saturday in France, also required vaccinated Americans to undergo frequent COVID tests, as U.S. vaccination cards were not considered sufficient proof to comply with European standards.

Many television series currently in production have been delayed or shut down due to positive COVID-19 tests on set. Hulu’s “Woke” suspended production twice in one week due to coronavirus outbreaks, while HBO paused production on “Westworld” for two days. Netflix’s “Bridgerton” and HBO’s “House of the Dragon,” the “Game of Thrones” prequel, also had to suspend production in the U.K.