A COMPARISON OF VACCINE EFFICACY AND MORTALITY DURING ROUTINE USE OF HIGH-TITER EDMONSTON-ZAGREB AND SCHWARZ STANDARD MEASLES-VACCINES IN RURAL SENEGAL

Vaccine efficacy and mortality in successive cohorts of children who r outinely received either Edmonston-Zagreb high-titre (EZ-HT) or Schwar z standard (SW-STD) measles vaccines have been examined in a rural are a of Senegal. The 2 vaccines were equally protective against measles i nfection (vaccination efficacy: EZ-HT 94%; SW-STD 93%). Children who d id not attend a scheduled session to receive measles vaccine had a hig her mortality rate between 9 months and 2 years of age than did childr en receiving either EZ-HT (mortality ratio [MR] = 1.81, 95% confidence interval [CI] 1.06-3.08) or SW-STD measles vaccine (MR=1.74, 95% CI 0 .95-3.21). Children of either sex vaccinated with EZ-HT had lower mort ality than their equivalents who had not received any measles vaccine. There was no difference in overall mortality between recipients of EZ -HT and SW-STD (MR=0.96, 95% CI 0.70-1.30). Using a Cox regression ana lysis to adjust for sex, age and significant background factors (seaso n and death of mother), mortality rates tended to be lower for male re cipients of EZ-HT than for boys receiving SW-STD (MR=0.73, 95% CI 0.50 -1.11) and higher for girls receiving EZ-HT than for girls receiving S W-STD (MR=1.30, 95% CI 0.81-2.09) (rest of interaction between sex and vaccine, P=0.067). The tendency to reduced survival benefit for girls following receipt of high-titre measles vaccines substantiated observ ations from randomized trials in Guinea-Bissau, Senegal, and Haiti. Ex isting data provide little support for the notion that high-titre vacc ine is deleterious bur it may not have the same beneficial effects as standard-titre measles vaccine.