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

States with high mandates are poised to uphold MMR requirements. California, New York, and West Virginia are strongly positioned to maintain their strict school-entry Measles, Mumps, and Rubella (MMR) vaccine mandates. This stance is robust even against the potential for less stringent federal guidance from the Advisory Committee on Immunization Practices (ACIP). These states have already removed all non-medical exemptions, a policy consistently supported by court decisions. Their legal foundation rests on state sovereignty under the Tenth Amendment, the enduring Supreme Court precedent of Jacobson v. Massachusetts from 1905, and firmly established statutory frameworks.

States possess primary authority over public health vaccination mandates. The power to establish public health mandates, particularly those for school entry, is largely reserved to the individual states. ACIP recommendations serve purely as guidance and do not constitute legally binding federal law. States such as California, New York, and West Virginia would assert that their existing statutes were enacted to address specific local epidemiological risks and public health crises. An example is the 2014 Disneyland measles outbreak, which directly led to California's SB277. Courts consistently apply a deferential "rational basis review" to public health laws, a standard these mandates are highly likely to satisfy, rendering successful legal challenges improbable.

Sustained high vaccination rates are essential for public health. The continued strength of these state mandates is directly linked to measles incidence, with any reduction in stringency inevitably correlating with a significant rise in cases. Epidemiological models indicate that a 95% vaccination rate is critical for robust community protection against measles. Should these states be required to reintroduce non-medical exemptions, vaccination rates would likely fall below this crucial threshold, creating conditions conducive to large-scale outbreaks. The successful defense of West Virginia's centralized medical exemption process against legal challenges serves as an effective model for how states can preserve policy integrity through strong administrative design and legal defense.

FY2026 Section 317 funding falls short of public health needs. The Senate Appropriations Committee has proposed $681.933 million for the CDC's Section 317 Immunization Program for Fiscal Year 2026, maintaining a nominal level of funding. This allocation significantly undershoots the estimated requirements, with the 317 Coalition assessing a minimum of $1.13 billion needed for adequate national immunization infrastructure support, and the CDC's own internal estimate exceeding $1.6 billion for full funding. While the President's initial budget concept proposed substantial reductions for the CDC, Congress ultimately countered this, securing approximately $9.2 billion for the agency, which effectively represents flat funding overall.

Inflation erodes Section 317's real purchasing power. Despite the nominal "level funding" for Section 317, an inflation-adjusted analysis reveals a significant reduction in real purchasing power. The FY2024 funding, when adjusted for an estimated cumulative inflation of 6.5% by FY2026, held a purchasing power equivalent to approximately $726.2 million in FY2026 dollars. Consequently, the proposed $681.933 million for FY2026 represents a real-dollar cut of about $44.4 million in purchasing power compared to FY2024. This decrease in real funding directly impairs the operational capacity of state and local health departments, which are essential for critical functions like vaccine distribution, administration, surveillance, and public outreach. The Vaccines for Children (VFC) program, while continuing to fund vaccine procurement as an entitlement, relies heavily on the diminishing infrastructure supported by Section 317 for its effectiveness.

Underinvestment threatens public health and outbreak preparedness. The consistent underinvestment in Section 317 funding creates substantial vulnerabilities for public health, particularly concerning the prevention of vaccine-preventable diseases such as measles. Direct consequences of these funding shortfalls include weakened outbreak response capabilities, the erosion of surveillance systems, and an impaired ability to effectively counter misinformation. This trajectory, compounded by proposed cuts to the broader Public Health Emergency Preparedness (PHEP) program, increases the likelihood of larger, more frequent, and more difficult-to-control outbreaks of highly contagious diseases between 2025 and 2028. Addressing these challenges necessitates strategic changes, such as implementing multi-year appropriations or establishing mandatory funding for immunization infrastructure.

The 2025-2026 measles outbreaks in South Carolina showed R0 values like past epidemics. These localized outbreaks exhibited a basic reproduction number (R0) ranging from 14 to 18, which mirrors the intrinsic transmissibility of the measles virus observed in pre-elimination eras . This high R0 was particularly evident in communities where vaccination coverage had significantly declined, allowing the virus to spread as it would in a completely susceptible population. By 2025, South Carolina’s statewide MMR vaccination coverage had fallen to 82%, significantly below the 95% threshold required to establish population-level herd immunity .

Declining vaccination rates created susceptible pockets, fueling the outbreak's spread. The degradation of herd immunity was clearly indicated by key metrics, such as the kindergarten two-dose MMR rates in South Carolina, which decreased from 95% in the 2019–20 school year to 91% in 2024–25 . In Spartanburg County, the epicenter of the outbreak, school-level vaccination coverage was approximately 90%, a situation exacerbated by a tripling of religious exemptions by the 2025-2026 school year . This clustering of unvaccinated individuals created sufficiently large susceptible pockets to sustain the outbreak, leading to 876 confirmed measles cases across South Carolina by February 3, 2026.

Major private health insurers and hospitals maintain MMR coverage without new mandates. As of early 2026, leading private health insurance providers including UnitedHealth Group, Aetna, Anthem, Cigna, and Humana, continue to offer comprehensive, no-cost-sharing coverage for the Measles, Mumps, and Rubella (MMR) vaccine. This policy extends through the end of 2026, driven by Affordable Care Act mandates and the insurers' own public commitments. However, these insurers have not implemented new mandates requiring vaccination as a condition of eligibility, nor have they tied premiums to vaccination compliance. Similarly, while pediatric hospital systems adhere to the American Academy of Pediatrics immunization schedule, they do not impose direct financial penalties for declining vaccination. Some individual practices may impact access to care, potentially refusing unvaccinated families, though this practice faces challenges from state-level legislation in jurisdictions such as Texas.

Falling MMR vaccination rates are causing significant measles resurgence. Despite widespread financial access to the vaccine, MMR vaccination rates are declining, with 16 states reporting coverage below the 90% herd immunity threshold during the 2024-2025 academic year. This decline has directly contributed to a substantial resurgence of measles, evidenced by nearly 50 outbreaks and over 1,800 cases recorded in 2025 alone. The economic burden associated with these outbreaks is considerable, with the average cost per measles case estimated at approximately $43,000. Projections indicate that if 2025 trends persist through 2028, the direct economic impact could reach $309.6 million, underscoring a critical gap between vaccine coverage availability and public health uptake.

Private healthcare cannot enforce vaccination standards without government action. The analysis concludes that the private healthcare sector is not currently positioned to enforce vaccination standards in the absence of strong government-led public health policy. Insurers primarily function as passive payers for a covered benefit, rather than active enforcers of public health protocols. Hospitals and clinicians are bound by professional ethics and, increasingly, by state laws that restrict their ability to refuse care to unvaccinated individuals. Consequently, the primary responsibility for preventing a continued resurgence of measles will fall squarely on public health agencies and state legislatures.

Permissive exemption policies can quickly drop MMR vaccination rates. Analysis indicates that if a state's MMR vaccination coverage is at or above the 95% herd immunity threshold, it could fall below this critical level within 4 to 8 academic semesters (2 to 4 years) following the implementation of more permissive non-medical exemption (NME) laws. This decline aligns with a broader national context where kindergarten MMR coverage has fallen from 95.2% pre-pandemic to 92.5% in the 2024-2025 school year, pushing the national average below herd immunity. This trend is further exacerbated by a rise in vaccine exemptions, which reached 3.6% nationally in 2024-2025.

Exemption policy type critically influences measles-mumps-rubella vaccination rates. States that have repealed all NMEs have demonstrated an ability to increase MMR vaccination rates by up to 4.0 percentage points within three years. Conversely, states allowing both religious and philosophical exemptions show the lowest average rates, experiencing a 3.8 percentage point decline from 93.3% to 89.5%. States permitting only religious exemptions also see declines, with rates falling by 2.3 percentage points from 94.4% to 92.1%. These findings consistently highlight how permissive policies correlate with lower vaccination coverage.

Current factors could accelerate future vaccination rate declines significantly. The present environment, marked by increased vaccine hesitancy and misinformation, suggests that historical lag times for declining vaccination rates may be conservative. Any future policy changes between 2025–2028 that weaken vaccine mandates could lead to accelerated declines compared to pre-2020 precedents. Crucial determinants of how quickly rates might fall include baseline vaccination rates, the specific type of policy change, and the post-COVID information landscape. Monitoring the rate of increase in exemption filings could serve as a leading indicator for proactive public health interventions.

The prediction market for measles cases during Trump's second term could be driven higher by several factors. The administration's emphasis on "personal freedom" regarding vaccination may lead to a reduction in routinely recommended vaccines and foster an environment against vaccine mandates, potentially decreasing uptake. Executive orders early in the term also indicated a shift in US public health policy, including potential defunding of federal agencies like the CDC and NIH, and a possible withdrawal from the WHO, which could significantly disrupt disease surveillance, research, and outbreak response. These federal actions compound an existing trend of declining US vaccination rates for MMR and an increase in exemptions, with more states relaxing childhood vaccine requirements. Such conditions could fuel persistent measles outbreaks, which are often imported through international travel among unvaccinated populations. Conversely, a reduction in measles cases could be influenced by increased public awareness stemming from significant ongoing outbreaks, which may encourage higher vaccination rates at local and state levels, independent of federal policies. State and local health departments, along with non-governmental health organizations, could launch robust campaigns to promote measles vaccination and combat misinformation, thereby increasing vaccine uptake. Additionally, scientific advancements in vaccines or improved vaccination practices could lead to better disease control, although a significant reversal of federal public health policy prioritizing vaccination and strengthening infrastructure is considered unlikely during the current administration.