December 22, 2025
Most people in Utah have been vaccinated against measles (more than 90%). If the vaccine wasn’t doing its job, we would see 90% of the infections happening in vaccinated people just because that’s who lives in Utah. Instead, only 6% of the Utahns who have gotten measles were vaccinated people. That shows the vaccine is working.
But obviously it isn’t 100% perfect. Some people may get infected even if they are vaccinated. As I said earlier, the measles vaccine is almost perfect but it’s not quite there (is anything?). About 3 people in 100 who are vaccinated and exposed to measles will get sick with measles. It is likely that many hundreds of vaccinated people have been exposed to measles in Utah, but the vast majority of them have been protected by the vaccine. We only see the few where their body was not able to fight it off.
In contrast, there is a small number of Utahns who have not been vaccinated (around 10%). Those people are also being exposed to the virus. Unlike the vaccinated Utahns, a majority of the unvaccinated Utahns get sick with measles. This is why we see so many unvaccinated people with measles even though they make up a small minority of our population.
Dr. Leisha Nolen, Utah state epidemiologist