How much vaccination is enough to stop measles?

AI SLAI HLAA SL Solid Also in: Statistics, Differential equations

Research question

Across countries, how is measles incidence related to vaccination coverage, and is there evidence of a threshold near the herd-immunity level predicted by R₀?

Adapt it: change the place, the data or the comparison until the question is yours.

Why it makes a good exploration

Measles is extremely contagious, so its herd-immunity threshold is very high. Comparing WHO data with the simple formula 1 − 1/R₀ links statistics with epidemic modelling.

The mathematics you'll need

Scatter plots with log-scaled incidence
Correlation and regression
Herd immunity threshold 1 − 1/R₀
Piecewise or threshold models

Course labels show where a technique sits; using maths from outside your course is fine if you explain it clearly and say it is new to you.

Where the data comes from

Coverage and reported cases by country and year from the WHO Global Health Observatory.

WHO Global Health Observatory — 1,000+ health indicators by country (immunisation, mortality, risk factors).
Our World in Data — Clean country-level time series (CO₂, population, health, energy, education) with CSV download on every chart.

Cite every source in a footnote where you use it and in your bibliography. Check the licence of any dataset you download.

A possible outline

Explain R₀ and herd immunity.
Plot incidence against coverage.
Model the relationship; test for a threshold.
Compare with the theoretical threshold.
Reflect on under-reporting, clustering and imported cases.

Pitfalls that cost marks

Treating countries as one population.
Ignoring reporting quality.
Logs of zero incidence.

Showing personal engagement

Look at your own country's history of outbreaks.
Explain clustering of unvaccinated groups.
Discuss the ethics of using this data carefully.

See Criterion C: personal engagement for what examiners look for.

Taking it further

Simulate an SIR model with vaccination and compare outbreak sizes around the threshold.

Turn this idea into your IA

Plan this IAOpens the planner with this question, the maths and data sources filled in. Desmos workspacePlot your data, fit models and keep your graphs with your plan. AI feedback on a draftCriterion-by-criterion feedback with evidence from your own text. Coaching, not rewriting. Examiner reviewPete, a practising IA examiner, reads your draft and talks it through with you (€100).