Vaccination rates among kindergarteners in the United States have been declining in recent years. Secretary of Health and Human Services, Robert F. Kennedy Jr., has expressed intentions to review the childhood vaccination schedule, raising concerns about the potential resurgence of measles and other infectious diseases that were previously eliminated. An analysis released by epidemiologists at Stanford University seeks to quantify these potential impacts.
Using a computer model, the researchers found that maintaining current state-level vaccination rates could result in measles reestablishing itself in the United States over the next two decades. The model indicated this outcome in 83 percent of simulations, predicting that the US could face over 850,000 measles cases, along with 170,000 hospitalizations and 2,500 deaths, over the next 25 years if current vaccination trends persist. These findings have been published in the Journal of the American Medical Association.
Jeffrey Griffiths, a professor of public health and community medicine at Tufts University School of Medicine in Boston, who was not involved in the study, commented on its validity. He noted that while the study is a modeling exercise, it is based on reliable data, emphasizing that measles is likely to become endemic again if current trends continue.
The US had declared measles eliminated in 2000 following decades of successful vaccination campaigns. Elimination implies there has been no continuous transmission of the disease in the country for over 12 months. However, an ongoing measles outbreak in Texas, with over 600 cases, 64 hospitalizations, and two deaths, threatens this status. This figure marks the largest outbreak in the state since 1992. Nationally, the US has reported 800 measles cases in 2025, the highest since 2019, compared to 285 cases in the previous year.
Mathew Kiang, an assistant professor of epidemiology and population health at Stanford University and one of the study’s authors, stresses the importance of increasing vaccination coverage as much as possible.
Childhood vaccination rates in the US have been decreasing. Data from the Centers for Disease Control and Prevention indicate that coverage for state-mandated vaccinations among kindergarteners declined from 95 percent to approximately 93 percent between the 2019–2020 and 2022–2023 school years. These vaccinations include the MMR (measles, mumps, and rubella), DTaP (diphtheria, tetanus, and acellular pertussis), polio, and chickenpox vaccines.
In their study, Kiang and his colleagues modeled each state individually, factoring in vaccination rates that ranged from 88 percent to 96 percent for measles, 78 percent to 91 percent for diphtheria, and 90 percent to 97 percent for the polio vaccine. Additional variables considered included demographics, vaccine efficacy, risk of disease importation, infection duration, the time between exposure and transmission, and the basic reproduction number. Measles is highly contagious, generally spread by one person to 12 to 18 people, and the model used 12 as the basic reproduction number.
