Figure 1.

(a) Weekly measles case reports for the province of Ontario, Canada, from 1939 through 1965. Data were digitized from unpublished, handwritten spreadsheets obtained from the Ontario Ministry of Health. The light grey line represents a moving average over the 24 months preceding and following each date. (b) Monthly live births for the province of Ontario, Canada, from 1939 through 1965. Data obtained from: Government of Canada, Dominion Bureau of Statistics, ‘vital statistics 1921–1966’. Both the weekly case reports and the monthly birth time series can be downloaded from the International Infectious Disease Data Archive (http://iidda.mcmaster.ca).