ABSTRACT
A study was conducted to determine the incidence of neurological complications among a cohort of 6,980 recipients of Semple vaccine administered in Bangkok and 5 nearby provinces in 1984. A review of all patients admitted to public hospitals in these 6 provinces discovered a total of 32 cases, with neurological complications following Semple vaccine. Twenty-two cases (68.8%) were encephalitis or myelitis. The complication rate was 3.6 times higher for males than females and the rate was lowest in the 0-14 year age group. Vaccinees receiving large daily dose of vaccine had a higher rate of complications than those with low dose regimen. One patient died, giving the case-fatality rate of 3.13 per cent. Since the search was limited, the rate of neurological complications to Semple vaccine was a minimum of 4.6 cases per 1,000 vaccinees [1:220]. This complication rate was much higher than most rates reported previously. It is imperative to find economically feasible alternatives to Semple vaccine.