 Warnings were made that an epidemic was imminent and Downs and Hill began a program of inoculating health workers and stockpiling vaccine.Trinidad health authorities followed up with large-scale vaccination and intensive anti-"aegypti" measures including public education, regular inspection for breeding sites, and spraying of domestic residences with DDT.In spite of these measures, and the fact that an estimated 80% of the population of Port of Spain were immune to yellow fever and dengue, several more cases were soon reported.