Report of 4 years' follow-up of a trachoma clinical trial in Taiwan.

Few widespread diseases show such marked local differences in community patterns as does trachoma; these differences occur not only in over-all prevalence but also in the mean age at onset, the age distribution of the evolutive stages and the role of associated infections. These are among the factors which determine the relative frequency of infections, reinfections and superinfections, and influence the long-term effects of a collective-treatment programme, especially when treatment is restricted to a circumscribed segment of the community.A therapeutic trial, carried out on first-grade primary-school children in Taiwan, gave immediate results in terms of rate of cure which were closely similar to those of an earlier trial on children in the same age-group in Morocco. However, 1 year after the withdrawal of treatment, the net reactivation rate was more than 25% in the Taiwan group compared with less than 2% in the Morocco group. Therapeutic trials in new territories should therefore be followed up for a sufficient length of time to assess the long-term therapeutic and prophylactic value of the treatment regimen in the population group concerned. The application of a clinical scoring system to the data from the Taiwan study provided an effective means for measuring changes in a pleomorphic disease picture which are not apparent from simple rates of cure.