Seroconversion after measles vaccination at 6 mo depends on whether maternal immunity was acquired by infection (V1) or vaccination (V2) (Ped Inf Dis J 1995, 14:17). In a double-blind trial, 60 V1 and 120 V2 infants received AIK-C and 120 V2 infants received CLL measles vaccine at 6 mo concurrent with DPT-Polio-Hib. MMR was given at 15 mo. The study group consisted of 153 boys and 147 girls and represented the local infant population with respect to race and economic background. Pre and post vaccination samples (6, 8, 15 and 17 mo) were tested for seroresponse by enzyme immunoassay (EIA) and plaque reduction neutralization tests (PRN) and for cell-mediated immunity by blast transformation (BT) to measles hemagglutinin (HA) antigen. Before measles vaccination at 6 mo 22% of V1 and <1% of V2 infants were seropositive by EIA (OD≥.200). At 8 mo, 33% of V1, 75% of V2 AIK-C and 88% of V2 CLL infants were seropositive by EIA. More infants were seropositive at 15 mo(preMMR) than at 8 mo (40% of V1, 86% of V2 AIK-C and 91% of V2 CLL). All infants were seropositive at 17 mo (postMMR). PRN data were consistent with EIA values. Cell mediated responses are expressed as the stimulation index(SI). 61% of V1, 73% of V2 AIK-C and 66% of V2 CLL infants had a 2-fold or greater SI in response to HA at 8 mo compared with the 6 mo sample. Seropositivity at 8 mo was not always accompanied by an increase in SI and vice versa. Although not statistically significant, breast-fed infants had lower spontaneous lymphocyte responses (unstimulated) and lower responses to HA antigen after 6 mo immunization compared with formula fed infants.
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Pabst, H., Spady, D., Carson, M. et al. Comparison of Immune Responses to AIK-C and Connaught (CLL) Measles Vaccines Given at Six Months of Age. † 753. Pediatr Res 41, 128 (1997) doi:10.1203/00006450-199704001-00773