This Centers for Disease Control and Prevention (CDC) scientist was preparing to test a patient’s sample for SARS-CoV-2, using the CDC 2019 Novel Coronavirus (2019-nCoV) Real-Time Reverse Transcriptase (RT)–PCR Diagnostic Panel. (James Gathany/CDC 2020)

Marin County’s surge in COVID-19 cases has started to plateau, a reflection of the county having the highest vaccination rate in California, the county’s top health official said Tuesday.

The county’s current surge, Marin County Public Health Officer Dr. Matt Willis told the Board of Supervisors, peaked at an average of roughly 51 cases per day in early August.

Since then, the average number of new confirmed cases per day has dipped to 40, while the county’s test positivity rate is under 4 percent for the first time since late July, Willis said.

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“I wouldn’t call that necessarily a reliable decline in cases statistically but it is certainly, I think, a reliable plateau in cases,” Willis said. “It is still a plateau of high transmission … but I think we can feel reassured that we’re not seeing that rapid increase that we had seen over July.”

The county’s overall average number of new cases per day per 100,000 residents is still high at 16.1. Among unvaccinated residents, the rate is much higher at 36.5 cases per 100,000 while the rate among fully vaccinated residents sits at 9.5 cases per 100,000.

Willis noted that, under the state’s now-defunct tiered reopening system, the county would be firmly in the most restrictive purple tier because of its case rate.

“That’s the kind of information we’ll be looking to, to determine when we might resume some things that we value so much, including gathering in-person for board meetings, maybe lifting some of the mask recommendations,” Willis said. “But really it’s too early to take those steps because we are still seeing significant rates of community transmission.”

Willis pointed to the county’s superlative vaccination rate as the main reason behind the plateau in cases. As of Tuesday, 95.5 percent of the county’s 233,313 residents age 12 and older have received at least one vaccine dose.

In addition, 88.3 percent of eligible Marin County residents are now fully vaccinated.

According to Willis, other counties across the state with vaccination rates above 70 percent are seeing their summer surge in cases slow much faster than those with rates below 70 percent.

“When we look across the state of California, 58 counties, what we see is there’s clearly an association between the velocity, the trajectory of increased cases and vaccination rates,” he said.

County officials have already taken steps to mandate vaccination locally, requiring proof of fully vaccination or weekly testing for first responders like law enforcement officers, firefighters and EMS personnel who work in or respond to calls at high-risk places like hospitals, jails and nursing homes.

All county employees are also required to confirm their vaccination status, but unvaccinated public sector workers are not required to test regularly for COVID-19.

Information about the COVID-19 vaccine can be found at