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hippyjoe1955 How vaccines work:
Pathogen enters → Innate immunity (first responders) fights crudely while adaptive immunity (specialized B/T cells) learns the enemy and makes memory cells.
Vaccine skips the danger: Delivers harmless antigen (e.g., measles spike protein) → Body builds antibodies and memory without sickness.
Next exposure: Memory cells destroy germ before symptoms hit. No vaccine is 100%—they prevent
severe illness, not always all infection.
A family from Ukraine moved to Canada. They got all the vaccines including measles etc when they landed in Canada. Two years later they all had the measles.
Key point: Unvaccinated fuel outbreaks with 1 unvaxxed case infects 12-18 others.
Vaccinated cases don't spark epidemics.This happens rarely (~2-5% breakthrough cases) because: No vaccine blocks 100%; MMR is 97% effective after 2 doses vs. severe measles.
Could be: First dose only (93% effective), waning immunity (rare), lab error, or mild case from vaccine strain (not wild virus).