THE EFFECT OF DOSE AND STRAIN OF LIVE ATTENUATED MEASLES-VACCINES ON SEROLOGICAL RESPONSES IN YOUNG INFANTS

High morbidity and mortality from measles among infants under 9 months of age is an obstacle to measles control in many developing countries . In this paper, we review 30 studies conducted on the serological res ponse to measles vaccine in infants aged less than 9 months. Among chi ldren aged under 9 months, Edmonston Zagreb and AIK-C vaccines produce higher seroresponse rates than Schwarz vaccine of equivalent titre. F or Edmonston Zagreb and Schwarz vaccine, seroresponse rates increase w ith increasing vaccine titre. The absolute rate of seroresponse to Edm onston Zagreb vaccine in 6-month old infants varied greatly between st udies because of differences in methods of vaccine titer measurement, serological assays, definitions of seroresponse, and maternal antibody profiles of the populations studied. Seroconversion rates to Edmonsto n Zagreb or AIK-C vaccines al 6 months of age were generally similar t o those to Schwarz vaccine at 9 months of age, but antibody levels wer e lower after vaccination below 9 months of age. Although the increase d mortality documented in other studies after use of high titer vaccin es in 4-6 month old infants led to withdrawal of these vaccines, this review of vaccine trials highlights the need for standardization of st udy methods and for a better understanding of the biological action of measles vaccines.