California's statewide indoor mask mandate kicks off as virus cases rise

California's statewide indoor mask mandate for over the Christmas holiday took effect on Wednesday.

State health officials announced the new mandate on Monday, citing a 47% increase in COVID-19 case rates across the state since Thanksgiving, State Health and Human Services Secretary Dr. Mark Ghaly said.

The mandate requires everyone in California to mask up indoors at public indoor settings, regardless of vaccination status, from December 15 through January 15.

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The new order also requires those who have not been vaccinated to show proof of a negative COVID-19 antigen test within one day of an event with more than 1,000 people or a negative PCR test within two days of the event. The previous rule required a test within 72 hours of the event.

State officials will also recommend, but not require, that people who travel to California or return to the state after traveling be tested for COVID-19 within three to five days.

Certain parts of the state, like Los Angeles County, already have an indoor mask mandate in place, but other parts of the state do not. According to Ghaly, roughly half of California's population lives in counties that already have an indoor mask-wearing requirement in place.

"As we look at the evidence that masks do make a difference, even a 10% increase in indoor masking can reduce case transmission significantly," he said.

San Francisco, however, is exempt from the rule. The city will continue to allow fully vaccinated people to remove their masks in gyms and workplaces while its overall masking mandate remains in effect, the city Department of Public Health announced.

"It’s a recognition of all of the thought and care that San Francisco residents have been putting into staying as safe as possible," said Dr. Susan Philip, San Francisco’s health officer.

About 86% of eligible San Francisco residents have received at least one vaccine dose, according to the public health department.

Dr. Ghaly did not share any information about an enforcement strategy for this new mandate, but "strongly recommended" local governments and businesses implement a strategy themselves in order to "save lives." 

State officials are afraid of a repeat of last winter, when the state averaged more than 100 cases per 100,000 people during a monster winter surge of the virus when nearly 20,000 people died during an eight-week period.

But that surge was before vaccines were available. Today, more than 70% of California’s residents who are eligible have been fully vaccinated against the coronavirus. Even with the recent increase in cases, the state is averaging a little more than 14 cases per day per 100,000 people.

Even so, Ghaly said hospitals in several counties with low vaccination rates are still struggling with lots of patients, including parts of Southern California in Riverside, San Bernardino, Mono and Inyo counties. Ghaly warned coronavirus hospitalizations often increase in the weeks following a jump in new cases.

"We are proactively putting this tool of universal indoor masking in public settings in place to ensure we get through a time of joy and hope without a darker cloud of concern and despair," Ghaly said. "Californians have done this before, and we of course believe we can do it again."

Tune in to FOX 11 Los Angeles for the latest Southern California news.

The Associated Press contributed to this report.