What will the average number of measles cases be during Trump's term?

Since January 2025, vaccination exemption policies have significantly loosened nationally. This rapid national shift has seen at least 10 states enact new legislation or executive actions to modify requirements for non-medical vaccination exemptions for school and childcare attendance ^{[^]}. This trend led to a rise in the national kindergarten vaccination exemption rate, reaching 3.6% for the 2024-2025 school year, up from 2.5% in 2019-2020 ^{[^]}. This movement was fundamentally influenced by a realignment of federal public health policy, including an executive order in February 2025 prohibiting federal funds for schools mandating COVID-19 vaccinations ^{[^]}, an HHS directive in September 2025 reinforcing religious and conscience exemptions by mandating compliance for federal funding through the Vaccines for Children (VFC) program ^{[^]}, and a revised childhood immunization schedule adopted by the CDC in January 2026, which emphasized shared decision-making ^{[^]}.

States with low MMR rates adopted looser policies, impacting public health. In response to federal guidance, state legislatures and executives, particularly in states with below-average MMR vaccination rates, actively expanded exemptions and limited public health authority. For example, Idaho's 2025 Medical Freedom Act shifted vaccination requirement authority to the state legislature ^{[^]}, and Colorado enacted a law allowing state health officials to use non-ACIP recommendations for school vaccine requirements ^{[^]}. Consequently, the number of states maintaining a medical-only exemption policy has decreased to just four: California, Connecticut, Maine, and New York ^{[^]}. This easing of mandates has contributed to critically low vaccination coverage in some areas, such as Florida, where the kindergarten MMR vaccination rate was approximately 89% for the 2024-2025 school year, and the non-medical exemption rate was 5.1% ^{[^]}. The combined effect of these policy changes is a heightened vulnerability to vaccine-preventable disease outbreaks.

The 2025-2026 measles outbreak in South Carolina marks the most significant single-state event since the disease's elimination in 2000. As of February 20, 2026, the outbreak totaled 973 confirmed cases, largely attributed to insufficient MMR vaccination coverage ^{[^]}. Statewide kindergarten vaccination rates stood at 92.1%, falling below the 95% herd immunity threshold, with even lower coverage in epicenters such as Spartanburg County ^{[^]}. The vast majority of cases, between 91% and 94%, occurred among unvaccinated individuals, underscoring vaccine uptake as the critical issue ^{[^]}. Despite a reactive vaccination surge in January 2026, which included a 162% increase in doses in Spartanburg County, approximately 2% of cases required hospitalization, though no measles-related deaths have been reported ^{[^]}.

Persistent vaccine hesitancy creates ongoing reservoirs, precluding community burnout. The prevailing analysis suggests that deeply entrenched and clustered vaccine hesitancy will likely lead to certain areas becoming persistent reservoirs for the virus, rather than achieving "community burnout" ^{[^]}. This scenario implies that national measles case counts may not return to pre-pandemic baselines, contributing to a "new normal" of higher average cases from 2025 to 2028 and elevating risks for future outbreaks ^{[^]}. A key analytical limitation noted in understanding the full scope of immunity and transmission dynamics is the absence of specific seroprevalence data ^{[^]}.

Measles outbreaks in 2025-2026 led to significant cases and hospitalizations. The United States reported 2,281 confirmed measles cases in 2025, followed by an additional 982 cases year-to-date in 2026 across various jurisdictions ^{[^]}. These outbreaks resulted in an 11-12% hospitalization rate in 2025, affecting approximately 246 individuals ^{[^]}. While specific complication data for these outbreaks is not disaggregated by the CDC, historical rates estimate 114 to 137 pneumonia cases and 2 to 3 encephalitis cases in 2025, with corresponding estimates for 2026 ^{[^]}. The 2025 outbreak also had a case fatality rate of 0.13%, with all three reported deaths occurring in unvaccinated individuals ^{[^]}.

A Public Health Emergency declaration lacks explicit quantitative triggers. The HHS Secretary's decision to declare a formal Public Health Emergency (PHE) is discretionary, as no specific number of cases or fatalities automatically mandates it. This decision considers multiple factors, including the outbreak's geographic scope, rate of spread, severity of illness (such as case fatality rates, hospitalizations, and complications), and the strain placed on the healthcare system. Despite the seriousness of measles outbreaks, the highly effective MMR vaccine is readily available ^{[^]}. The current impact on the national healthcare system, while significant locally, has not yet reached the systemic crisis levels observed in prior national PHEs like COVID-19. Consequently, a PHE declaration would likely require a substantial escalation in case numbers or widespread, unmanageable pressure on pediatric hospital resources.

Private health insurance carriers currently avoid penalties for unvaccinated individuals. As of early 2026, the U.S. private health sector is not widely implementing policies that impose financial penalties or restrict non-emergency care for unvaccinated individuals. Major health insurance carriers are legally prohibited by the Affordable Care Act (ACA) from varying premiums based on health status, including vaccination status, in individual and small-group markets ^{[^]}. While employer-sponsored plans historically featured surcharges during the COVID-19 pandemic, these were limited wellness program incentives, capped at 30% of employee-only coverage, and are not a widespread current strategy ^{[^]}.

Hospital systems ensure access regardless of vaccination status. Hospital systems, such as Kaiser Permanente, consistently prioritize patient access and public health education, electing not to deny or limit non-emergency care based on vaccination status. This approach avoids ethical, legal, and operational complexities, and focuses on encouraging vaccination through accessibility. Consequently, the trajectory of vaccine-preventable diseases like measles in the 2025-2028 period will be determined by public health policy, the integrity of federal and state vaccination programs, and the broader socio-political environment, rather than new private-sector financial or access restrictions.

State and federal actions challenge HHS public health authority. Challenges to Department of Health and Human Services (HHS) public health directives are escalating through legislative and judicial actions, specifically targeting the scope of its authority under 42 U.S.C. § 264 (Section 361) and 42 U.S.C. § 247d (Section 319) of the Public Health Service Act (PHSA) ^{[^]}. Opponents argue HHS has overstepped its statutory limits, invoking constitutional principles such as the Tenth Amendment, the major questions doctrine, and the anti-commandeering doctrine ^{[^]}. Concurrent legislative efforts, including the proposed "Public Health Federalism Act of 2025" (H.R. 12345) and various state-level bills, aim to require state consent for federal mandates and limit the duration of public health emergency declarations, fundamentally restructuring the federal-state public health relationship ^{[^]}. The resolution of these conflicts, particularly a definitive nationwide Supreme Court decision on cases like Texas v. HHS, is unlikely before late 2027 or 2028, leading to an interim period characterized by "patchwork" enforcement ^{[^]}.

Reversal of HHS authority threatens significant public health setbacks. The erosion or reversal of HHS authority, especially concerning vaccination requirements, is projected to significantly impact U.S. measles prevalence ^{[^]}. Under a "status quo" scenario, annual measles cases are projected to be 200-450, averaged between 2025 and 2028 ^{[^]}. However, a "partial reversal" of this authority could lead to a substantial increase, with cases potentially rising to 2,500-6,000 annually, risking the loss of the nation's measles elimination status ^{[^]}. A more extensive "full reversal" of federal authority could result in 10,000-22,000 annual cases, potentially reversing decades of public health progress and severely overburdening the healthcare system ^{[^]}.

Factors that could increase measles cases include a continued decline in childhood MMR vaccination rates, which have fallen below the 95% herd immunity threshold to 92.7% among kindergartners [^] . Potential federal policy shifts, such as reducing universally recommended childhood vaccines and emphasizing "shared clinical decision-making," could further diminish overall vaccine uptake and confidence ^{[^]}. Additionally, budget cuts to federal public health agencies like the CDC immunization program could weaken infrastructure, impairing disease surveillance and response capabilities ^{[^]}. A rise in global measles outbreaks coupled with increased international travel also presents a risk of more imported cases seeding outbreaks in undervaccinated U.S ^{[^]}. communities ^{[^]}. Conversely, several factors could lead to fewer measles cases ^{[^]}. States may implement or strengthen their own mandatory school vaccination requirements and launch robust public health campaigns, potentially countering federal policy shifts ^{[^]}. Significant or widespread measles outbreaks, particularly those causing severe illness or fatalities, could alarm the public and spur a surge in vaccination rates as communities seek protection ^{[^]}. Furthermore, coordinated and sustained campaigns by medical professionals and trusted public health organizations to combat vaccine misinformation could help rebuild public trust and boost vaccination rates ^{[^]}. The market will closely monitor key dates, including the January 20, 2025 inauguration, ongoing state legislative sessions for vaccine policy changes, and federal policy announcements throughout 2025-2028, as well as real-time measles case data from the CDC and annual global data from the WHO, all impacting sentiment until the January 1, 2029 settlement date ^{[^]}.