Measles has made a troubling comeback in the U.S. as MMR vaccination rates have fallen.<\/p>\n
But the same vaccine protects against two other viruses \u2014 mumps and rubella. So why haven\u2019t they made a similar resurgence?<\/p>\n
\u201cThe simple answer is that measles is the canary in the coal mine,\u201d said Allegheny Health Department medical director Dr. Jillian Irwin. \u201cMeasles is significantly more contagious than mumps or rubella.\u201d<\/p>\n
The rate of MMR vaccine adherence among U.S. kindergartners declined<\/a> from 95.2% during the 2019-2020 school year to 92.4% for the 2025-2026 school year (the most recent data available).<\/p>\n Mumps and rubella, however, don\u2019t spread nearly as easily and have lower herd immunity thresholds. That helps explain why falling MMR vaccination rates have allowed measles to emerge first \u2014 and why health experts warn mumps and rubella could follow if vaccination rates continue to decline.<\/p>\n In a susceptible population, one person with measles will generally infect 12 to 18 people. For mumps and rubella, that number is around four to seven, according to AHN infectious disease specialist Dr. Tom Walsh.<\/p>\n \u201cIf you think about vaccination as building a firewall around our community, as the vaccination rates fall, holes begin to open up,\u201d Irwin said. \u201cAnd measles is so contagious that it can find the smallest holes and move through them very quickly. Mumps and rubella just cannot do that as efficiently, so it takes certain circumstances for them to cause a problem or a larger outbreak.\u201d<\/p>\n Measles is a virus that infects the lungs and spreads via breath, coughing and sneezing. It remains in the air and on surfaces for up to two hours, even after an infected person moves on. An individual with measles can spread the virus to others four days before and four days after a distinctive rash presents. Symptoms typically start seven to 21 days after exposure.<\/p>\n Mumps can be spread through the air, but because the virus does not linger in the air like measles, it is spread primarily through direct contact with mucous and saliva. Symptoms start 16 to 18 days after exposure, and it\u2019s typically contagious for two days before and five days after it causes the salivary glands to swell. Its herd immunity threshold is 75 to 86%, according to the CDC.<\/p>\n