DENVER Colorado health officials on Tuesday confirmed the states first measles case of the year in a vaccinated individual in Broomfield County, underscoring just how contagious the virus can be if given room to spread.The stat es latest measles case the fourth for Broomfield County and the 10th tied to an ongoing outbreak in the area was confirmed by the Colorado Department of Public Health and Environment Monday after lab results came back positive for the viral infection.The CDPHE had suspected the individual was likely infected last week since they live in the same household as three other confirmed cases and had a prolonged exposure to the virus. That prolonged exposure is sometimes linked to a higher probably of breakthrough cases, according to a CDPHE spokesperson who provided a few more details about the case to Denver7.Statewide measles data shows the individual was only vaccinated with a single dose of the measles, mumps and rubella vaccine, which is 93% effective against measles, according to the U.S. Centers for Disease Control and Prevention. That protection increases to 97% with two doses of the shot.Given the scope of the outbreak and the number of cases so far this year, its likely Colorado will see a few more infections among vaccinated individuals this year. In 2025, an unvaccinated international traveler who landed at Denver International Airport ended up spreading the virus to 17 other people, 10 of whom had received at least one dose of the MMR vaccine. Denver7 has been closely following confirmed measles cases in Colorado amid a multi-state outbreak in the U.S. that began last year. Explore the map by clicking here or check it out below to see where cases have popped up in 2026:Federal and state health officials say that vaccinated individuals who do end up getting measles are less likely to spread the virus to others and will develop what researchers have termed modified measles, which typically involves milder disease.Though the number of measles infections among vaccinated individuals is likely to grow, it will pale in comparison to the number of infections among unvaccinated people. Last year, only a third of all measles cases in the state were among vaccinated individuals, according to statewide data.The latest case could have exposed hundreds of other people at the Bout Time Pub Grub sports bar, located at 5225 W. 80th Ave in Arvada on Tuesday, March 10, and Wednesday, March 11, between 8 p.m. and 12:30 a.m. Those exposed at that location may develop symptoms through April 1, according to the CDPHE.In Broomfield, people exposed to the virus at Bromfield Heights Middle School, Broomfield High School, two health care settings and a Chick-fil-A could develop symptoms through the end of day Wednesday.People in Louisville and Westminster should still monitor for symptoms if they visited any of the locations outlined in the CDPHEs measles exposure location website through at least Thursday.Anyone who develops symptoms between now and then should call the CDPHE at 720-653-3369 or your local public health agency immediately by phone before trying to seek treatment to avoid other people from becoming potentially infected with the virus. If you do not have a provider, the CDPHE urges you to call an urgent care center or emergency department and explain that you may have been exposed to measles.While most people recover within two or three weeks after contracting the virus, unvaccinated people run the risk of complications from the disease, including ear infections, seizures, pneumonia, immune amnesia, brain damage and ultimately, death.Measles only spreads from people who show symptoms; it does not spread from people who arent feeling sick, state health officials said.Unvaccinated people exposed to the virus can get the MMR vaccine 72 hours after exposure (but before symptoms are present) to prevent an infection, according to health officials. Immunoglobulin (IG), if administered within six days of exposure, may also be used in some circumstances, they added.We recommend children receive two doses of MMR vaccine, as per the American Academy of Pediatrics. Adult vaccine recommendations vary by their risk level, the CDPHE spokesperson said, adding that most adults without immunity to the virus should receive at least one dose of MMR vaccine. While two doses are recommended to increase immunity levels, a person is still considered vaccinated with one dose of the MMR vaccine, they wrote.Coloradans who frequent high-risk locations, such as health care settings, colleges and universities and those who frequently travel internationally should get two doses of the MMR vaccine, the CDPHE spokesperson said.People who got vaccinated against measles before 1968 should talk to their health care provider about possibly getting a booster as the vaccine used before that year wasn't as effective.As of Tuesday, Colorado has reported cases of the virus in Adams (5), Arapahoe (1), Broomfield (4), and Weld (1) counties. Over the past decade, the state has seen between zero and two cases each year. That changed last year, when Colorado reported 36 measles cases amid a multi-state outbreak of the virus in the U.S.Nationally, he number of confirmed measles infections has already topped 1,300, which already represents 60% of all measles cases the U.S. reported in all of 2025. ...read more read less