What will the average number of measles cases be during Trump's term?
I estimate a 40% probability that the market's “Yes” outcome will resolve; this reflects a moderate chance of sustained or increased measles incidence in the U.S. across 2025–2028 driven by global resurgence and domestic undervaccination pockets, tempered by public-health countermeasures and uncertainty about the market's exact resolution criteria.
Analysis
**Stage 1 — Blind analysis (ignore market price):**
- Context and baseline: Historically the United States has had very low annual measles counts since widespread vaccination, with notable exceptions such as the 2019 outbreak (~1,200–1,300 cases). The COVID-19 period temporarily suppressed importations and reduced reported case counts, but global measles incidence rebounded in many regions after 2020 because of disrupted childhood immunization programs.
- Key epidemiological drivers during 2025–2028 (independent of price): - *Importations*: Measles in the U.S. is principally fueled by imported cases from countries with ongoing outbreaks. As international travel returns to pre-pandemic volumes, importation risk increases. - *Domestic susceptibility pockets*: Low MMR coverage in geographic or social clusters (certain communities, some schools, some states with permissive exemption policies) creates the conditions for local outbreaks from relatively few importations. - *Public health response capacity*: Rapid outbreak control (case finding, post‑exposure vaccination, school exclusion) can limit size and duration of outbreaks; federal funding, state-level responses, and local health department staffing matter. - *Vaccine coverage trends*: If childhood MMR coverage recovers quickly after COVID-era declines, population susceptibility will fall; if coverage remains depressed or declines further, risk of larger outbreaks rises.
- Probabilistic assessment (blind): Given the combination of increased global incidence in recent years, restored travel, persistent pockets of undervaccination in the U.S., and variable public-health responses, I assess a moderate but not high chance that average annual U.S. measles cases across 2025–2028 will be substantially above the very low pandemic-era levels. Quantitatively, a ~40% probability that whatever threshold the market’s "Yes" proposition uses (likely tied to an elevated average vs. recent low baseline) will be met is a reasoned central estimate. This balances the realistic chance of multiple moderate outbreaks (driven by importations + clusters) against the deterrent effect of routine immunity in the general population and effective outbreak containment.
**Stage 2 — Market calibration (look at current market prices):**
- Current market price: Yes = 0.33, No = 0.67.
- My independent probability (40%) is higher than the market's 33% by 7 percentage points. Possible reasons the market is priced lower: - *Anchoring to pandemic-era lows*: Many traders may be anchoring to the very low reported case counts of 2020–2022 and underestimating the trajectory of global measles resurgence post-2021. - *Underweighting importation + cluster risk*: Non-expert traders might assume high national vaccination coverage makes large domestic outbreaks unlikely, thereby discounting the outsized effect of localized undervaccination. - *Unclear resolution wording*: Ambiguity about exactly how the average is calculated (calendar year vs. rolling average; inclusion/exclusion rules) might push risk-averse traders toward the safer No side, reducing Yes liquidity. - *Overconfidence in public-health countermeasures*: The market may overestimate federal/state capacity or willingness to mount large vaccination drives or school exclusion policies, which suppresses perceived risk.
- Implication for traders: If you share my view that global measles activity and restored travel will increase importations and that undervaccination pockets remain large enough to sustain outbreaks, the market appears slightly mispriced toward No. If you instead believe rapid recovery of routine childhood MMR coverage and strong outbreak containment will prevail, the market price is reasonable or even conservative for Yes.
- Caveat: The market’s exact proposition text matters materially. My independent probability is conditional on interpreting the event as measuring a materially elevated average (i.e., above pandemic lows or a pre-specified threshold). If the market’s threshold is unusually high or low, my calibration should be adjusted accordingly.
Arguments
For
- Increased international travel post‑COVID raises the probability of measles importations, the primary spark for U.S. outbreaks.
- Global recovery gaps in routine immunization after the pandemic have led to large outbreaks in multiple countries, increasing sustained importation risk over several years.
- Clusters of undervaccinated individuals in the U.S. remain (by community, school, or state) and can amplify importations into measurable outbreaks.
- If federal or state policy does not aggressively close immunization gaps, susceptibility will persist and allow larger outbreaks when seeded.
Against
- High baseline MMR coverage in the general U.S. population provides herd immunity that limits the size and frequency of large nationwide outbreaks.
- Public-health systems have recent experience responding to outbreaks and may successfully limit spread through rapid case investigation, quarantine/exclusion, and targeted vaccination drives.
- If routine vaccination rates rebound quickly after COVID-era disruptions, the susceptible population will shrink substantially over 2025–2028.
- The market may define its threshold for 'Yes' at a level that requires very large outbreaks (e.g., annual averages above 1,000+) — an outcome that remains relatively unlikely given historical context.
Key drivers
- Global measles incidence and outbreaks in source countries (importation risk)
- Domestic MMR vaccination coverage and recovery after COVID-era disruptions
- Size and location of undervaccinated clusters (schools, communities, states)
- Volume of international travel and migration patterns during 2025–2028
- Public-health detection, outbreak response speed, and federal/state funding/policies
Risk factors
- Persistent lower-than-expected MMR coverage in certain U.S. communities leading to susceptibility pockets
- Large, sustained outbreaks overseas that increase the frequency of importations
- Reduced public-health workforce capacity or funding that slows response and containment
- Ambiguities in the market’s resolution (averaging method, date range, inclusion rules) that increase uncertainty about what outcome satisfies 'Yes'
Scenarios
Best case
Widespread recovery in routine childhood MMR vaccination coverage across the U.S., combined with targeted public-health campaigns and rapid outbreak response, keeps annual cases very low. Importations occur but are contained to single-digit or low-double-digit events per year; the observed average across 2025–2028 is below the market’s triggering threshold, producing a No resolution.
Most likely
A middling outcome: several importations per year and a few localized outbreaks (tens to low hundreds of cases) occur across 2025–2028. These cause variability year-to-year but result in a modestly elevated multi-year average compared with 2020–2022 lows. Whether that average satisfies the market’s Yes threshold depends on the precise numeric cutoff; overall probability of Yes ~40% by my independent assessment.
Worst case
Large measles epidemics occur in multiple source countries and travel rebounds fully; several importations seed outbreaks in undervaccinated U.S. communities, leading to multiple large clusters (hundreds to >1,000 cases in a year). Weak or slow public-health responses and persistent low coverage in key pockets allow sustained transmission, producing an average measles case count across 2025–2028 well above historical baselines and a Yes resolution.
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