"In County buildings we are requiring vaccinated and the unvaccinated to wear masks," said San Mateo County Supervisor David Canepa.
The latest COVID data is what's driving this mask requirement inside their county facilities.
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"One step forward and a half step backward. I guess you could view it that way but in my mind it's better to be safe than sorry. I think it's probably the right move," said San Mateo resident Todd Master.
A month ago their test positivity rate was 0.4%. Now, it's 2.6%.
"We've seen an uptick in our cases in the last two weeks. They nearly doubled," said Canepa.
They're attributing that increase to the Delta variant. Now accounting for 83% of COVID cases statewide.
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Birgul Polat is a San Mateo county resident and a nurse at San Francisco general hospital seeing firsthand the impact of the Delta variant. She agrees with this mask requirement.
"I don't think people know how serious it is," said Polat.
Recently, San Mateo along with six Bay Area counties urged residents to wear facemasks indoors.
RELATED: Bay Area counties recommend indoor mask wearing, even if vaccinated
In LA county, masks are required indoors also regardless of vaccination status.
"I think maybe we dropped the mask mandate a little too quickly," said Burlingame resident, Scott Matt.
Inside Chic beauty salon in downtown Burlingame, the mask mandate was never lifted.
"I'm not ready yet and all my clients come here and they still wear their mask," said Linda Danc, Nail technician at Chic Salon.
Supervisor Canepa says they are following the data closely before making any additional changes.
"It's the first step and it's a small step. We will see what we can do moving forward if we have to take additional action," said Canepa.
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