From Monday, residents of San Mateo County will be required to wear masks indoors despite 89 percent of the population being fully vaccinated.

The mask mandate has been brought back in San Mateo County “out of an abundance of caution” as the Delta variant spreads through the county and the rest of California.

According to the official figures, San Mateo recorded 13 new COVID-19 cases on June 15 as the state lifted restrictions. By July 15, the number of cases had risen to 74, a trend the country describes as “troublesome.”