SUMMARYThe epidemiological, clinical and virological features of 1220 children with acute bronchiolitis admitted to the Prince of Wales Hospital, Hong Kong, from 1985 to 1988 are reported. They accounted for 6·6% of total paediatric admissions and provided a case incidence of bronchiolitis requiring admission to hospital of approximately 21 per 1000 children 0–24 months of age.The clinical course and outcome was in general benign. The average hospital stay was 5 days and there were no deaths. Ten per cent of patients were repeatedly admitted to hospital with recurrent wheezing after discharge. Two infants developed bronchiolitis obliterans.Respiratory syncytial virus (RSV) was shown by direct immunofluorescence, virus culture and serology to be the commonest cause of acute bronchiolitis in Hong Kong. Other aetiological agents included parainfluenza and influenza viruses, adenoviruses, and Mycoplasma pneumoniae.In contrast to western countries, a seasonal variation of bronchiolitis was found with a peak incidence in the summer months. The significance of these observations is discussed.

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SUM/MARYVaccines were prepared from a single pool of high-titred vaccinia virus and inactivated by six methods, namely heat, formalin, hydroxylamine, f8-propiolactone, ultraviolet irradiation, and visible light and methylene blue. Large doses of the vaccines were required to protect mice against intracerebral challenge. Differences in protection were not attributable to the method of their inactivation. The vaccines also induced similar degrees of skin immunity in rabbits which showed no severe dermal reactions when challenged with either homologous killed vaccine or live virus. The virus-neutralizing, haemagglutinin-inhibiting and complement fixing antibody responses to the vaccines differed; heat-inactivation preserved these antigens least well and f8-propiolactone apparently the best. In both rabbits and mice there was little association between the different antibody responses to each vaccine or between the degrees of antibody response and the protection they induced. The relation of these findings to pox-virus immunity and the use of inactivated smallpox vaccine in man is discussed.