The measles epidemic in Calgary 1969-70; the protective effect of vaccination for the individual and the community.

Twenty per cent of the city's population of 375,000 had had live measles vaccination as pre-school children in the preceding four years. Protection rates for killed-live vaccine schedule (Edmonston) and live vaccine only (Schwarz) were approximately 66%, not diminishing in four years; the rates for killed vaccine only (three doses) were similar for 18 months, diminishing later. As the numbers who have acquired immunity by contracting the disease fall by 10 percentage points, numbers immunized by live vaccines must rise by 15 percentage points to maintain an equivalent balance of immune and susceptible subjects.