July 15, 9 a.m. Health officers in Yolo County issued an advisory Wednesday calling on all residents—even those who are fully vaccinated—to wear masks in public indoor settings due to increasing spread of the highly transmissible Delta variant. The advisory is a recommendation and not mandatory. 

“Vaccinated residents are strongly recommended to wear masks in indoor settings where vaccination verification is not required and the vaccination status of others is unknown,” said health officers. “Unvaccinated individuals are still required to wear masks in indoor public spaces.”

This announcement comes after Los Angeles County started recommending masks in indoor public areas, regardless of vaccination status. 

California Gov. Gavin Newsom said last week there was no immediate plan to implement a statewide requirement. 

“If we continue to get people vaccinated that’ll be unnecessary and this is the call that anyone who hasn’t been vaccinated get vaccinated,” said Newsom, as reported by ABC 7 News.

The Delta variant, also known as B.1.617.2, accounts for 58% of new COVID-19 cases across the country, according to the Centers for Disease Control and Prevention. 

Since mid-April Yolo County has detected 59 cases of the Delta variant, according to the statement from the county. The variant made up to 76% of positive samples collected on the UC Davis campus and through Healthy Yolo Together testing between June 27 and July 7.

“In making yesterday’s new recommendations for fully vaccinated persons to resume masking indoors and to get tested after an exposure, I am erring on the side of caution to slow the spread of the highly infectious Delta variant,”  said Yolo County Health Officer Dr. Aimee Sisson in a statement. “Vaccines remain the absolute best form of protection against COVID-19, and I implore everyone who is eligible to get fully vaccinated as soon as possible. At the same time, we know that our vaccines, while highly effective, aren’t perfect. Putting on a mask indoors in settings where you can’t be sure that everyone who is unmasked is fully vaccinated is a simple way to add another layer of protection against COVID-19.”