IMMUNE-RESPONSE TO MEASLES-VACCINE IN 6-MONTH-OLD INFANTS OF MEASLES SERONEGATIVE MOTHERS

Determinants of measles vaccine-induced immune response in infancy inc lude maternal immune status and the infant's age at immunization. In a previously published study, 74% of 19 6-month-old infants developed n eutralizing antibody. Two of the infants were born to measles seronega tive mothers(1). In older to (1) assess the prevalence of measles sero negativity in a population of US mothers born after 1960 and (2) asses s the immunogenicity of standard titer measles vaccine in 6-month-old infants of measles seronegative mothers, mothers with healthy term (gr eater than or equal to 37 weeks gestation) infants attending well chil d care clinics at MetroHealth Medical Center were prospectively screen ed for measles antibody by EIA. If negative maternal samples were rete sted for neutralization (NT) antibody, Fifteen of 169 women were seron egative by both assays. Six-month-old infants of 9 of these 15 seroneg ative mothers were enrolled in the pediatr ic vaccine study Serologica l response of these 9 infants to monovalent measles vaccine (Attenuvax o) was compared to the responses of 17 6-month-old infants of seroposi tive mothers and 15 15-month-old toddlers from our previous study, All 9 infants of seronegative mothers became ELA seropositive after the v accine compared to 9 of 17 B-month-old infants born to seropositive mo thers (p = 0.02). Differences in NT seroconversion rates (100% vs 70.6 %) were not statistically Significant. The comparison group of 15-mont h-old vaccinees showed 100% seroconversion by both assays, The NT geom etric mean titer (GMT) was higher in the 15-month-old toddlers than in the 6-month-old infants born to seronegative mothers (87.2 vs 33.9, p < 0.01), suggesting age-related differences in humoral immune respons e unrelated to passively transferred en maternal antibody. (C) 1998 El sevier Science Ltd. All rights reserved.