Herd Immunity & Vaccination Coverage Simulator

Preventive medicine's most effective tool is immunization: when enough of a population is immune, an outbreak can no longer sustain itself even without treating every case. This simulator populates a crowd of agents — susceptible, pre-vaccinated, or seeded with a handful of initial infections — and lets an epidemic play out in real time. Infected agents spread the disease to nearby susceptible agents at a rate set by the basic reproduction number R₀, then recover and become immune after their infectious period ends. Adjust vaccination coverage, R₀, population size and infectious period to see the outbreak curve grow, peak and fade, and watch how coverage above the herd-immunity threshold 1 − 1/R₀ can stop a disease from taking hold at all.