Marin County announced Tuesday the region has seen two recent outbreaks tied to the highly contagious Delta variant.
Dozens of unvaccinated people were infected, but the situation would have been more severe if the county didn’t have a highly successful vaccine effort. This week, Marin reached the milestone of 90% of eligible residents receiving one or more doses. The county has the highest vaccine rate in the Bay Area.
“With 90% of the population vaccinated, these outbreaks were limited, ” said Marin Health Director Dr. Matt Willis. “In the past these could have easily triggered surges that would have continued to grow. Instead, they were by and large surrounded by individuals who are protected and so the outbreaks died. This is what community immunity is. It’s encouraging to see the protection the vaccine is offering. It’s also a caution that those who are unvaccinated remain vulnerable with the Delta variant circulating.”
The first outbreak occurred in the adjacent towns of San Anselmo and Fairfax where 30 COVID-19 cases were reported, all in unvaccinated individuals who were eligible for inoculation. One patient infected with the Delta variant was hospitalized and recovered. While the county didn’t identify the specific variant in every case, those that were sequenced showed the Delta strain.
The second outbreak rose in June from a school in Novato where 25 cases were identified, with some in unvaccinated children who aren’t eligible for the vaccine due to their age.
“It was centered in the school, and then in people who were connected to the school through sports programs or social networks,” said Willis.
Both outbreaks were controlled within 14 days and are no longer active, the county said.
“It offers a glimpse of what the next stage of this pandemic will look like with variants spreading among unvaccinated groups,” said Willis. “How widely it spreads is dependent on the number of people in the community who are vaccinated.”
He added, “When clusters of cases rise and fall quickly among unvaccinated people, and don’t really spread further, this is what herd immunity looks like. We’re seeing what community immunity could look like in Marin. The current cases are among unvaccinated residents, which is why we’re motivated to get closer to 100%.”
The Delta variant, which is more infectious and potentially more deadly than other variants, now represents more than 20% of coronavirus infections in the U.S. in the last two weeks, or double what it was when the Centers for Disease Control last reported on the variant’s prevalence.
Dr. Anthony Fauci, the nation’s top infectious disease expert, warned that the U.S. could be following the United Kingdom’s course, where the variant has become the dominant strain due to rapid spread among youth. Fauci said indications are that the COVID-19 vaccines remain effective against the variant. The B.1.617.2 variant was first identified in India.
In Marin, 70% of cases that have been sequenced in the past month were the Delta variant.
“The takeaway is that this variant really has legs,” Willis said. “It does move quickly when it finds groups of unvaccinated people. Fortunately, in Marin that number is very small.”
The Associated Press contributed to this story.