A study was undertaken to assess the effectiveness of a yellow fever vaccination campaign, which had been conducted in Trinidad, West Indies from November, 1978 through 1979.

Evaluative tools consisted of:

(i) an interview survey in a randomly selected sample of two hundred households, to determine immunization coverage and (ii) a serological study of 232 vaccines to ascertain protection conferred through use of 17D yellow fever vaccination. Results of the household survey indicate that approximately 12.53 per cent of the 1149 persons interviewed had not been vaccinated against yellow fever. In most instances, no substantial reasons could be advanced by respondents for non-immunization. Based on the performance of 13 plaque reduction neutralization tests, all but one of the 232 sera examined from people with a history of immunization posessess adequate humoral immunity to yellow fever. This study has, therefore, shown that the vaccination campaign, under review, was successful in achieving satisfactory protection of immunized persons, and in drastically reducing the number of susceptibles within the population.