Study warns measles could become endemic in US as vaccination rates continuously fall

A new study from Stanford University warns that declining childhood vaccination rates in the US could result in the resurgence of measles and other once-eliminated infectious diseases.

The study uses computer modelling to project the potential outcomes of continued low vaccination coverage. According to the model, if current trends persist, measles could become endemic in the US within 20 years — meaning it would circulate continuously, rather than appearing in isolated outbreaks. The findings of the study, which come at a time of increased measles outbreaks across the US, have been published in the Journal of the American Medical Association and reported on by Wired publication. 

The result is alarming as it finds that measles reestablished itself under current vaccination conditions in 83% of simulations. The model estimates over the next 25 years that the US could see 850,000 measles cases, 170,000 hospitalizations, and 2,500 deaths if vaccination rates do not improve. Measles was officially declared eliminated in the US in 2000, a status that may now be in jeopardy. The ongoing outbreak in Texas — with more than 600 cases, 64 hospitalizations, and two deaths — is the largest since 1992. Nationally, 2025 has already seen 800 measles cases, surpassing the 285 recorded in 2024.

Childhood vaccination coverage in the US has steadily declined in recent years. According to the Centers for Disease Control and Prevention (CDC), vaccination rates among kindergartners dropped from 95% in the 2019–2020 school year to around 93% in 2022–2023. Vaccines tracked included MMR (measles, mumps, rubella), DTaP (diphtheria, tetanus, pertussis), polio, and chickenpox.

The Stanford researchers, led by Nathan Lo and Kiang, accounted for several variables in their model: state-by-state vaccination rates, population demographics, vaccine efficacy, risk of disease importation, infection timelines, and disease contagiousness. Measles, one of the most contagious viruses, has a basic reproduction number of 12 to 18, meaning one infected person can transmit the virus to up to 18 others. The study used 12 as its base estimate. 

The model showed that even small changes in vaccination coverage can have dramatic effects. A 10% drop in measles vaccination rates could lead to 11.1 million cases over 25 years, while a 5% increase would reduce expected cases to just 5,800. In addition to measles, the model assessed the risk of rubella, polio, and diphtheria — diseases no longer endemic in the US due to widespread vaccination. With their lower basic reproduction numbers, these diseases are less likely to become endemic unless vaccination rates fall sharply.

Rubella, for instance, would require a 35% drop in coverage to reestablish itself in 81% of scenarios, and polio had a 50% chance of becoming endemic if rates declined by 40%. Diphtheria was deemed the least likely to return. The study’s authors caution that the consequences of falling vaccination rates may not be immediate. "It’s totally feasible that vaccinations go down and nothing happens for a little while," Kiang explains. "But eventually, these things are going to catch up to us." 

By Nazrin Sadigova