Analysis of the secular trend and seasonal variation of measles mortality rate in Taiwan.

The secular trend and seasonal variation of measles mortality rate in Taiwan from 1959 to 1981 were analyzed through multiple regression analyses. A significant downward trend with a regular two-year cyclic fluctuation was observed before and after the implementation of a mass vaccination campaign, and the difference between odd and even years was greater in later years than in earlier years. There was a characteristic unimodal pattern of seasonal variation which peaked in the months of late spring or early summer, and measles deaths were found more clustered in epidemic years than in nonepidemic years. While 94.3% of the total variation of annual measles mortality rate could be explained by calendar year, two-year cycle, and their interaction; 87.6% of the total variation of monthly measles mortality rate could be explained by calendar year, two-year cycle, month, and the interaction between two-year cycle and month. The implication and application of such multiple regression analysis of temporal components of measles epidemiology are discussed.