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Concern around measles as WA kids head back to school
Officials are urging families to check immunization records before heading to school to protect vulnerable populations, noting that King County offers online resources to find no-cost vaccines.
KING COUNTY, Wash. - As students return to the classroom for the new school year, health officials in King County are closely monitoring measles vaccination rates, warning that some local schools and districts have fallen below the threshold required for herd immunity.
Public Health – Seattle & King County reports that only 92% of King County kindergartners have received their complete set of measles, mumps, and rubella (MMR) vaccines. Achieving community, or herd, immunity against measles requires a 95% vaccination rate.
While the gap may appear narrow, health experts emphasize the serious public health implications of falling short of that target.
The math behind the risk
By the numbers:
Measles is an exceptionally contagious airborne disease. The virus spreads through coughs and sneezes and can remain active in the air for up to two hours after an infected person leaves a room. Furthermore, infected individuals can transmit the virus at school, home, and social gatherings before they even begin showing symptoms.
According to the Centers for Disease Control and Prevention (CDC), even slight drops in coverage significantly increase the risk of a community outbreak.
In a school or community of 1,000 children, a 92% vaccination rate means that 80 children remain unprotected. Scaled up to Seattle Public Schools alone—which enrolls roughly 4,000 kindergartners—that percentage translates to approximately 320 unprotected students.
Public health officials note that unprotected children often cluster in specific communities, creating pockets of vulnerability that accelerate the spread of disease.
Vulnerable populations at higher risk
A drop in community protection places the most vulnerable residents at heightened risk. This includes infants who are too young to receive the vaccine, pregnant individuals, and people with compromised immune systems.
The backstory:
Washington state has experienced similar threats in recent years. In 2019, Clark County recorded 16 measles cases, prompting a local state of emergency. While case numbers dropped significantly between 2020 and 2022 due to social distancing measures during the COVID-19 pandemic, Southwest Washington recorded nine cases in 2023. Low-level or sporadic activity followed in 2024 and 2025, preceding a national surge and subsequent imported cases to parts of Western Washington.
Official guidance and resources
Despite the mounting concerns, health leadership emphasizes that a local outbreak is not guaranteed.
What they're saying:
"We are very concerned about the spread of measles in King County." " said Dr. Sandra J. Valenciano, Director and Health Officer for Public Health – Seattle & King County. "While most King County residents, including school-aged kids, are protected against measles through vaccination or prior infection, some schools and school districts are below the 95% MMR vaccination rate needed for herd immunity. Measles is one of the most contagious infections we know of, meaning it can easily take-hold in communities with low vaccination rates and cause outbreaks. Our most vulnerable residents – infants too young to have been vaccinated yet, people with compromised immune systems, and pregnant people – are at the greatest risk."
What you can do:
Public health agencies are urging families to check vaccination records and ensure children are fully immunized before heading back to school. For families seeking coverage, King County provides online resources, including a map locator to help find locations offering no-cost vaccinations for children and uninsured adults.
The Source: Information in this story comes from Public Health – Seattle and King County and original reporting by FOX 13 Seattle's Taylor Winkel.
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