Is Santa Cruz’s reported vaccine rate inaccurately low? It just might be because of this UCSC-related quirk

A close look at ZIP code data provided by the California Department of Public Health for vaccinations in Santa Cruz County shows a curiously low number for 95064, home to UC Santa Cruz.

While the state reports only 17.8% have been vaccinated, which would make it one of the least vaccinated ZIPs in California, UCSC officials say the true number for the university community is actually north of 90%.

UCSC spokesman Scott Hernandez-Jason said students often use their home addresses for vaccination purposes, potentially explaining the disparity.

According to the university, students had a vaccination rate of 95.6% as of Nov. 30, while faculty and staff had a rate of 91.3%.

And county health officials say this could be happening for not only students, but for anyone who has an official address in Santa Cruz but claims for any number of reasons a different one when getting a vaccine in a different county. Though they know it’s happening, they acknowledge it’s impossible to know how widespread it is.

All that adds up to the fact that the county’s overall vaccination rate of 69.5% — one of the lowest of its neighbors — might not be fully accurate. As of Tuesday, Santa Clara County was 79.4% fully vaccinated and San Mateo County was 77.4%, though Monterey County was at 65.6%.

The raw data from the state lists the population 5 years and older for the 95064 ZIP code as 10,440, with 1,756 being fully vaccinated. Using the university’s figure of 95.6% — and operating under the assumption that the vast majority of people in that ZIP code are students — the number of fully vaccinated people jumps to 9,881.

This, in turn, pushes the county’s overall rate to 74.9%, an increase of more than 5%.

Hernandez-Jason said all students, faculty and staff have to submit proof of vaccination to attend classes or work. Under UCSC policy, the only exemptions are for a medical condition, religious belief, disability or pregnancy. The university received proof of vaccination from all students who planned to attend classes in person and staff who go to work.

Representatives from the university, county and state said there’s a simple reason for the difference in rates between the state’s records and the university’s data.

“CDPH reports vaccination rates based on recipients’ reported addresses of residence, so it is possible that students using their permanent addresses in their vaccination records are being attributed to other counties,” the state health department’s communications office said in an email.

However, officials at the state agency did not respond to questions about whether this might be happening at other college campuses, and how it would affect overall vaccination rates.

Regardless, the discrepancy, while large, doesn’t appear to have an impact on how county public health officials prevent the spread of COVID-19 on the campus.

Ramy Husseini, the health services manager for the Santa Cruz County communicable disease and population health units, said the county works closely with university officials and receives vaccination information from the California Immunization Registry — the system that records California residents’ vaccine and ZIP code data.

The data is particularly important for contact tracing and case investigation. When someone becomes a positive case, one of the county’s case investigators reaches out to the newly positive case and has their vaccination status and lab information checked through the state’s CalCONNECT system.

This system is connected to the state’s immunization registry, and case investigators are able to verify a person’s vaccination status regardless of where they were vaccinated in the state.

“So even though they may have been vaccinated elsewhere — let’s say someone lives in L.A. County, but they’re a student here, and they’re living on campus — we would have the information at the ready,” he said.

The state’s data has nothing to do with the county’s response in this scenario.

Husseini said it’s also likely that the entire county, not just the UCSC ZIP code, is seeing a lower vaccination rate than what the rate is in reality.

For example, some people who reside in Santa Cruz County are seeking vaccines outside of the county, according to Husseini. He added that it’s nearly impossible to know how many people are doing this, but officials know it’s happening. While officials have not heard from people why they would be traveling to get vaccinated, Husseini said it could be due to people working in other counties or because other counties had more shots available at a certain time.