Measles cases in Texas and New Mexico have surged to 351, with experts warning the outbreak could persist for years due to declining vaccination rates.

But there's a silver lining, officials say: More people have received a measles, mumps and rubella vaccination this year in Texas and New Mexico, which also has an outbreak, compared to last year — even if it's not as high as they would like. And pharmacies across the U.S., especially in Texas, are seeing more demand for MMR shots.

Vaccination efforts have faltered, and many residents have turned to alternative treatments endorsed by Robert F. Kennedy Jr., the health secretary.