The epidemiology of Japanese encephalitis on Taiwan during 1966-1997

Japanese encephalitis (JE) is an endemic disease in Taiwan. A mass vaccinat ion program of children against JE was first implemented in 1968. Along wit h general improvements in various aspects: of living conditions over the ye ars, the program has brought JE well under control. The main characteristic s of JE epidemiology in Taiwan in the past 3 decades are as follows. The tr ansmission mode remains unchanged-that is, the amplification stage of the v irus in pigs is followed by a human epidemic each year. The frequency of JE incidence has dropped significantly. The incidence rate of confirmed cases was 2.05 per 100,000 in 1967, the highest in record, and merely 0.03 per 1 00,000 in 1997. Confirmed cases occur sporadically all over the island. The peak of the epidemic season has shined from August in the 1960s to June si nce the 1980s. The age distribution of confirmed cases has shifted graduall y from mainly children to adults. Vaccine efficacy for those having receive d more than 2 doses of the vaccine is estimated to be about 85%.