Health officials, even in the Bay Area, are split.
Dr. Bela Matyas is the public health officer for Solano County, and is an outlier among Bay Area health officials when it comes to supporting mask mandates.
"The experiment would show that the mandate isn't making a difference in disease transmission," Dr. Matyas told ABC7 News.
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Dr. Matyas said Solano County can be looked at as a microcosm for understanding masking. In recent months, only Vallejo and Benicia had mask requirements. The rest of the county, including Fairfield and Vacaville, did not.
"Ironically, the disease rates are higher in the two cities with the mandate than the two cities without. Not uniformly, but on average," he explained.
Data provided to ABC7 News by Solano County health officials show there was no correlation between the cities with the mandates and those without.
Between Sept.1 and Dec. 4 of this year, Vallejo -- which had a mask mandate in place -- had a case rate of 1,213.
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The case rate in Fairfield, which did not have a mandate, was lower at 1,035.
However, Vacaville, which also did not have a mask mandate, had the highest case rate at 1,470.
Those numbers line up with the public data on the county website. It also shows that throughout the entire pandemic, Vacaville has had the highest case rate, followed by Vallejo and then Fairfield.
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From those numbers alone, it's hard to conclude a mask mandate led to a decline in cases. But health officials have mixed opinions.
California's Health and Human Services Secretary Dr. Mark Ghaly told reporters this week that masking in public spaces does make a difference.
"As we look at the evidence, does masking make a difference? Even a 10% increase in indoor masking can reduce transmission significantly," Dr. Ghaly said.
Dr. Grant Colfax, San Francisco's Public Health Director, said mask mandates are about using all the mitigation efforts at our disposal.
"Masking is another tool that we have to help slow the spread of this virus. So, I think it's important we all continue to mask," he told ABC7 News.
While Dr. Matyas said that might be true, he believes the real spread of COVID-19 is happening not in public spaces, where there will be a mask mandate, but in private among friends and family.
"That's where the disease was spreading," he said. "It wasn't spreading walking through a clothing store or a hardware store."