West Marin vaccination rates are high, but the county admits its numbers are somewhat unreliable. The county as a whole boasts one of the highest vaccination rates in the nation, surpassing 90 percent of the eligible population last week. But understanding rates in rural Marin is complicated by two factors: the county’s listing of rates by census tract rather than by town, and the presence of populations that are difficult to capture in census estimates.

Data on vaccination rates is available on the Marin County Health and Human Services’ website, where it is grouped by census tract; West Marin, with its low population density, has only four tracts. None of the communities meet the minimum population requirement of 1,000 residents for releasing local data on Covid-19 vaccinations or case rates. Dr. Lisa Santora, the county’s deputy public health officer, said the requirement protects individuals “where it might be easier to discern who’s been vaccinated and who hasn’t.” 

Overall, vaccination rates along the coast are higher than the county expected. “We think West Marin’s done very well,” she said. “Traditionally it’s been a more hesitant area.”

The county provided the Light with data by clusters of towns to reach the threshold for reporting, allowing a more granular look at the vaccination rate. 

The combined rate of vaccination with at least one dose for Bolinas, Stinson Beach and Muir Beach is 87 percent. West Marin’s two other clusters are higher. Tomales, Marshall and Dillon Beach have a combined rate of over 90 percent, as do Inverness, Point Reyes Station and Olema.

The vaccination rate for the towns of Inverness, Point Reyes Station and Olema is on par with the high rate countywide, but it differs significantly from the corresponding rate for the larger census tract that includes just Inverness, Olema and the Point Reyes National Seashore. That rate is under 70 percent, but the county cautioned against reading too much into that number. 

Although the numbers of vaccinated individuals are accurate and exact, the overall population counts per census tract or town are based on American Community Survey estimates. Because the county is measuring vaccinations so precisely, it’s exposing the flaws in those population estimates.

“Our numerator is not connected to our denominator,” Dr. Santora explained. 

To explain the stark difference between the Inverness, Olema and the Point Reyes National Seashore census tract’s rate and the towns’ rates, Marin Health and Human Services analyst Haylea Hannah offered a few suggestions. 

Point Reyes Station has an especially high rate of vaccination, so when combined, she said it inflates the lower vaccination rate of the towns of Inverness and Olema, and the agricultural community in the seashore.

A few factors might account for the difference in rates between Point Reyes Station and these communities. One is the high proportion of second homes in Inverness. Though part-time residents should have completed the census at their primary residence, some did not. 

Dr. Matt Willis, the county’s public health officer, said if these individuals were vaccinated outside of the county, “They may be counted as an Inverness resident, but if they get vaccinated in Stockton, may be counted as a Stockton vaccinee.” 

About 18 percent of Marin residents who were vaccinated got at least one dose outside of the county, he said. 

Ms. Hannah also said that although A.C.S. estimates are the best population data the county has, they have a “great deal of uncertainty around them” in West Marin. 

Undercounting in the census contributed to the uncertainty. All four of these West Marin census tracts were in the bottom 20 percent of self-response rates for the 2020 census nationwide. As of last October, both the Inverness and Point Reyes Station tracts had response rates of about 43 percent, as compared with rates higher than 75 percent in San Anselmo, Larkspur and Mill Valley. 

When doing census outreach, “We needed to really include all of the West Marin census tracts,” said Stephanie McNally, the director of advocacy and policy at the nonprofit Canal Alliance. 

Between the number of vacant housing units that are used as second homes or vacation rentals, the number of residents who get mail at P.O. boxes rather than home addresses, and the number of houses without broadband internet, it’s difficult to get an accurate count. As a result, she’s concerned about the accuracy of the high vaccination rates being reported in West Marin, and suspects the real numbers are probably lower. 

Madeline Hope, the director of the Tomales Bay Youth Center, observed that there will always be a few West Marin residents who avoid vaccinations.

Yet between individual towns in the area, she does not see significant differences in attitudes toward the vaccine. “I don’t think people in Inverness are more or less hesitant than people in Point Reyes,” she said. 

So what is the takeaway about West Marin vaccine rates? Low density and poor population estimates make tracking them difficult, but the numbers are high overall and on par with the county’s progress. 

With 90 percent of Marin residents vaccinated, Dr. Willis believes that for the remainder, the issue is now less about access and more about belief. 

“It’s going to take us longer to reach people who are making decisions that they don’t yet want to get vaccinated,” he said. “That’s part of the long game.”

Health care providers and mobile vaccination units are still at work. While those units had a lot of ground to cover earlier in the process, he said if a team now returns having vaccinated only five people, that’s okay. 

As of this week, there are 45 active cases of Covid-19 in Marin, and no one is hospitalized with the virus. The county is continuing to monitor for outbreaks and variants, but it has demobilized its mass vaccination sites and is turning its focus to helping get people vaccinated worldwide. “It’s time to consider global equity at this point,” Dr. Willis said. 


To access your vaccination record, and to get an electronic copy of your record and QR code, visit myvaccinerecord.cdph.ca.gov.