Dr Lisa Santora, deputy head of public health for Marin County, said the outbreak includes 10 cases “inside and outside of school.”
The county declined to identify the “index case” or the perpetrator of the outbreak.
“It is safe to say that the index case was an unvaccinated person who was eligible for vaccination,” said Dr Matt Willis, county public health official.
“All cases are unvaccinated individuals,” added Willis. “This includes people who were eligible to be vaccinated but not vaccinated and people who were not eligible to be vaccinated, due to their age.”
Many students at private K-8 school are not vaccinated because they are under 12, the lower threshold for vaccinations.
School officials could not be reached for comment. Officials from the Archdiocese of San Francisco, which oversees some parish schools in Marin, did not respond to requests for information.
Willis said his staff are monitoring and testing whether any of the infected were involved in social gatherings outside of school or playing on local sports teams. He declined to specify a timetable for these activities.
“The tests are based on individuals who have been determined to have been exposed,” Willis said. “I can’t fit into any specific group. “
Kris Cosca, superintendent of the Novato Unified School District, said no cases had been reported in his schools, but some of his students could have been reported. He said 23 at-risk students had been “sent home to quarantine”.
“Contact tracing determined that some students at San Ramon Elementary School were potentially exposed to COVID while attending a private school in Novato, participating in youth sports, or by their siblings in one of these two contexts, ”Cosca said. “Contact tracing has shown that the positive cases identified to date are not the result of exposure at San Ramon Elementary School.”
Willis said the cluster of infection was the highest incidence to date in schools in Marin since the county started tracking viral data from schools last September. Prior to this week, there had been just 12 cases of school-based transmission in Marin’s 117 schools for nearly 2.5 million student days.
“The kids who shared these classrooms were also bonded socially and also bonded to sports teams,” Willis said. “The location of the transmission is still being determined. “
He said Marin had a person in the hospital with COVID and that person was not vaccinated. Another COVID patient, who was not vaccinated, died earlier a few weeks ago. All other cases of infection seen in the county are unvaccinated people.
“The best way to protect ourselves and the others around us is to get vaccinated,” Willis said.
“We cannot rely on high vaccination rates around us for our personal protection,” added Willis. “It is true that we have a very effective tool to prevent such epidemics – it is the vaccine.”
Willis said the outbreak could impact Marin’s plans to move next week from his current status of orange to yellow in the state’s follow-up plan. The state is requiring counties to have two or fewer cases per day per 100,000 residents for two consecutive weeks – a standard the county was meeting until this week.
While the Novato cases could prevent the county from advancing, “we’ve made so much progress elsewhere that we could move forward,” Willis said.
Marin has the highest vaccination rate of the state’s 58 counties.
“It’s great that we have the highest vaccination rate, but every unvaccinated person remains at risk,” said Willis. “It’s a sign of that.”
The state’s color-coded tier system, known as the Blueprint for a Safer Economy, will be phased out on June 15.