Chicago health officials say city’s measles outbreak is over

(CHICAGO) — The Chicago Department of Public Health (CDPH) declared the city’s recent outbreak of measles over on Thursday.

CDPH said 42 days have passed — two full incubation periods for measles — without any new cases confirmed.

On March 7, 2024, Chicago health officials confirmed the city’s first measles case in five years. Additional cases were confirmed in children and adults at a new arrivals shelter in Pilsen, on the lower west side of the city.

Over the course of the outbreak, 64 people in Chicago tested positive for measles, including 57 associated with Chicago shelters.

The CDPH said it collaborated with federal and local health care and community partners and “mobilized a rapid response of symptom screenings for shelter residents, detailed contact tracing, and isolation of people with suspected or confirmed measles,” according to its announcement.

Since the beginning of the outbreak, more than 30,000 doses of the measles, mumps and rubella (MMR) vaccine have been administered to Chicago residents, according to CDPH.

The Centers for Disease Control and Prevention (CDC) currently recommends two doses of the MMR vaccine, with the first dose given between ages 12 to 15 months and the second dose administered between ages 4 and 6. Adults are eligible to receive one dose of the vaccine if they are not immune.

One dose of the measles vaccine is 93% effective at preventing infection if exposed to the virus. Two doses are 97% effective, according to the CDC.

“The MMR vaccine is safe and by far the most effective way to protect yourself and others from future measles outbreaks, especially as tourism and travel ramp up over the summer months,” CDPH Commissioner Dr. Olusimbo Ige said in a statement. “Our goal is the elimination of measles in Chicago and everywhere, and with proper vaccination coverage, we know that zero is possible.”

Measles was considered eliminated in 2000 because most Americans were vaccinated against the disease or had some level of immunity. Over the last several years, however, vaccination rates have dipped and pockets of unvaccinated and undervaccinated communities have led to sporadic outbreaks across the U.S.