Colorado prevented measles outbreak from infected traveler
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Key takeaways:
- Quickly isolating a traveler with measles and effective contact tracing prevented an outbreak in Colorado.
- MMR vaccine coverage in Colorado is 86.8%, below the goal of 95% coverage.
A CDC investigator described how Colorado was able to prevent a measles outbreak after identifying an infected traveler who passed through the Denver airport, a children’s hospital and a community gathering while infectious.
The traveler, an adolescent with unknown vaccination status from a country where measles is endemic, was in Colorado for a week in December 2023 and was triaged, isolated and diagnosed with measles at the Children’s Hospital of Colorado, investigators reported at the CDC’s Annual Epidemic Intelligence Service Conference.
Globally, measles cases rose by nearly 20% in 2022, and nearly 33 million children missed a measles vaccine dose that year, according to data reported by the CDC and WHO. The CDC in January issued an alert to U.S. health care providers after dozens of cases were reported between December 1 and Jan. 23.
Although the MMR vaccine is highly effective at preventing measles, MMR coverage among kindergarteners has declined in recent years — falling nationally from 95% to 93% during the 2022-2023 school year — and in Colorado in 2023, it was 86.8%, according to the investigators.
As a result of lower MMR coverage, state and local public health officials moved quickly to issue a message to health care providers, notify the public and begin contact tracing to determine how many people had been exposed.
“It was a bit complicated as the patient had arrived in Colorado and had been in multiple counties during the infectious period,” Cara C. Drehoff, DVM, MPH, a CDC Epidemic Intelligence Service officer embedded with the Colorado health department, told Healio.
“One of the first steps we took when we were informed by the hospital that they suspected measles was to immediately start establishing a timeline of where that patient had been and when,” she said.
The adolescent arrived in Colorado on Dec. 13, 2023, at Denver International Airport, then traveled through several counties in the state before arriving at Children’s Hospital Colorado on Dec. 18, 2023. Based on their symptoms and history of travel, measles was immediately suspected, Drehoff said.
Colorado’s state public health laboratory confirmed the infection on Dec. 19, and public health officials immediately initiated contact tracing.
Drehoff and colleagues classified exposed contacts as immune, susceptible, unknown or unknown but likely immune based on birth year, military service or immigration status. On Dec. 20, a public health mobile unit tested and vaccinated household contacts and a public health MMR vaccination clinic was opened in the community.
Overall, the investigation identified 313 exposed contacts — 195 were immune, 37 were susceptible, 19 had unknown status but were likely immune, 37 had unknown immunity and 25 were lost to follow-up — but no secondary cases. However, 54 people received postexposure prophylaxis, 12 received immune globulin and 42 received the MMR vaccine.
“The best way we can prevent measles outbreaks is to ensure that we have high rates of MMR vaccination,” Drehoff said. “Colorado historically has had lower rates of vaccination among our school aged children, so we were really responding with urgency to the detection.”
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Drehoff CC, et al. Response to Measles in an International Traveler — Colorado, December 2023. Presented at: Epidemic Intelligence Service Conference; April 23-26, 2024; Atlanta.
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