Immune Amnesia0Erase 20–70% of previously acquired antibody memory
Morbidity vs Mortality Disparity
The 1962 Paradox: Pre-vaccine US mortality was reported as "2 per million overall population" (~400–500 deaths/yr). However, because measles infects 95%+ of all children without a vaccine, that mortality rate derived from over 4,000,000 annual infections, leading to 48,000 hospitalizations, 4,000 encephalitis cases, and thousands with permanent brain damage or deafness every single year.
At R₀ = 12–18, measles spreads via airborne aerosol particles lingering in airspace for up to 2 hours. Only achieving the ≥95% MMR herd immunity threshold prevents transmission chains from reaching vulnerable infants and immunocompromised agents.