San Mateo County has recorded two confirmed measles cases in 2026, and with classes starting as soon as Monday, August 10, health officials are urging local families to verify their children's vaccination records before the school year begins.
The San Mateo-Foster City School District's 10,500 students return August 10. The San Mateo Union High School District, which serves 8,700 students at San Mateo High, Hillsdale High, Aragon High, and eight other campuses, starts Wednesday, August 12.
Both districts require two doses of the MMR (measles, mumps, rubella) vaccine for enrollment. California has not allowed personal belief exemptions since January 1, 2016. Only medical exemptions, issued through the state's CAIR-ME system, are accepted.
A national surge hits close to home
The U.S. has confirmed more than 2,260 measles cases as of Tuesday, July 21, already approaching the 2,289 reported in all of 2025, according to CDC data reported by the Mercury News. The 2025 total was higher than the combined count for the previous 25 years.
California has logged 52 cases this year. Of those, 49 involved people who were unvaccinated or whose vaccination status was unknown, Bay City News Service reported from a Tuesday, July 21, news conference held by Bay Area health officials.
San Mateo County's two cases include one linked to a traveler who returned from abroad and visited a Burlingame restaurant in late February, prompting a county health advisory on February 27.
Public health resources stretched thin
"In our response to these two cases, we learned firsthand how resource-intensive a response to a single measles case can be," Dr. Farrell Tobolowsky, deputy director of the Communicable Disease Branch at the San Francisco Department of Public Health, said at the Tuesday, July 21, news conference.
Tobolowsky said that if San Francisco faced two or more simultaneous cases, her department would need to pull in additional staff to contain the spread. Federal funding cuts, she added, compound the challenge.
Measles is extraordinarily contagious. In a room with one infected person, nine out of 10 unvaccinated people will contract the disease, according to the CDC.
Local vaccination gaps
Statewide, more than 96% of California kindergartners were vaccinated for MMR in 2024-25, exceeding the 95% herd immunity threshold, according to the Public Policy Institute of California. But pockets of non-compliance exist locally. An EdSource investigation published January 28 found that five of six Burlingame Elementary School District schools landed on the state's vaccination audit list for the 2023-24 school year. At McKinley Elementary, roughly a third of 101 kindergartners lacked required vaccinations.
The San Mateo County Office of Education estimates about 20,000 children in the county cannot be immunized because they are too young or immunocompromised. Those children depend on high community vaccination rates for protection.
What families should do
California law requires proof of immunization at kindergarten entry, at seventh-grade advancement, when transferring from out of state, and for ninth- through 12th-grade admission. For the 2026-27 school year, an MMR titer test no longer satisfies the requirement, according to SMUHSD immunization documents. Two actual vaccine doses are needed.
Schools found out of compliance with state immunization rules can lose average daily attendance funding for students who are not fully vaccinated.
Families who need to schedule vaccinations before the August 10 and August 12 start dates can contact their pediatrician or check the San Mateo County Health website for clinic locations.
