In January 2025, a measles outbreak erupted on the western edge of Texas and soon spilled over to New Mexico and other states. The overall outbreak would become the largest the country has seen since 2000, when measles was declared eliminated from the US. In Texas, it was the largest outbreak recorded since 1992. And in New Mexico, it was the first measles outbreak the state had even seen since 1996.

But the trajectory of the two states’ measles cases diverged. Texas declared the outbreak within its borders over on August 18, with an end tally of 762 cases. In New Mexico, officials declared its outbreak, which began in February, over on September 26, with a total of just 99 cases.

One of the key differences, according to a new study, was that in New Mexico, the rapid spread of the highly infectious virus spurred a massive surge in measles vaccinations among children and adults. Overall, shots of the measles, mumps, and rubella (MMR) vaccine increased 55 percent statewide from January to September compared to the same period in 2024.

The study, appearing in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report, further broke down the increase in shots. Over the whole year, the number of MMR doses given to children (defined as less than age 18) increased 18 percent compared to 2024—from 27,988 in 2024 to 32,890 in 2025. Doses in adults (aged 18 and up) skyrocketed by a whopping 291 percent— from 5,748 in 2024 to 22,500 in 2025.

The increase in vaccination didn’t appear to be an unrelated fluke. Health officials noted that within two weeks of the outbreak being declared, the number of vaccine doses given in all regions of the state began to exceed the number given during the previous year. And in some regions, when a first measles case was identified, officials saw week-over-week increases in vaccinations as high as 78 and 83 percent.