Safety and efficacy of yellow fever vaccine in children less thanone-year-old.

In a clinical trial of stabilized yellow fever vaccine from Institute Pasteur in 77 children aged seven to eight months, fever was the most significant immediate and delayed side effect. Fever occurred in 12 (15.6%) children with in 48 hours of vaccination while it occurred in 10 (12.9%) children within ten days of vaccination. Other recorded side effects were pain at innoculation site in four (5.2%) children and vomiting in one (1.3%) child. Temperature recorded in 20 of the 22 febrile episodes ranged from 37.8 degrees C to 38.6 degrees C. One of the two patients who had temperatures of 39 degrees C and above had malaria parasites in her blood film. All episodes of fever except one responded to antipyretic. There was no episode of febrile convulsion and no feature suggestive of encephalitis. Of the 20 children who had neutralization test carried out against yellow fever virus six weeks after vaccination, the test was positive in post vaccination sera of 12 (60%) children whose pre-vaccination sera were negative. Two others showed evidence of partial protection. Although the seroconversion rate of 60% is less than reported in adults and older children, the result of this study shows that yellow fever vaccine is safe and fairly effective in infants. It is our suggestion that if a larger trial confirms our findings, the vaccine may be incorporated into the expanded programme on immunization (EPI) to be given at the age of seven months after completion of diptheria, tetanus, pertussis and poliomyelitis vaccinations and before measles vaccination is due.