Delaware health officials (DPH) reported two additional measles cases on Wednesday, bringing the state total to four, prompting the declaration of an outbreak (three or more cases of measles that are connected by time and location).
The measles cases identified to date are unvaccinated adult males in Kent County.
Extensive contact tracing is ongoing to identify anyone exposed to the individuals who tested positive. DPH will notify people who were identified as exposed to confirm whether they have been vaccinated against measles, provide educational resources, and to recommend treatment when necessary. More information will be forthcoming if contact tracing reveals any known public exposures.
The Delaware Division of Public Health recommends unvaccinated individuals or those unsure of their vaccination status who get exposed to a person with measles should contact their primary care provider or a public health clinic to obtain an MMR vaccine.
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Delawareans are encouraged to confirm their vaccination status as well as the status of their children.
The MMR vaccine is proven safe and effective at preventing measles having been administered for over five decades. Testing shows the MMR vaccine to be 97% effective at preventing measles for those who have received two doses of the MMR vaccine and are not severely immunocompromised. Children should get their first dose of vaccine between 12 and 15 months of age and their second dose between 4 and 6 years of age. If you have not received both doses by age 6, you should get your first or second dose as soon as possible. Infants 6 to 11 months who are traveling internationally or who are in an area experiencing a measles outbreak or exposure should receive one early dose of MMR vaccine.
In addition this week, the CDC reported the nationwide total of 2,318 confirmed measles cases were reported in the United States in 2026, as of July 23. This tops the 2,289 confirmed measles cases reported in all of 2025 in the US.