Reduced Antibody Response to Infant Measles Vaccination: Effects Based on Type and Timing of the First Vaccine Dose Persist After the Second Dose.

BACKGROUND: The effect of age at first dose on the immunogenicity of a 2-dose pediatric schedule of measles-mumps-rubella (MMR) or measles-mumps-rubella-varicella (MMRV) vaccine was assessed in children born to mostly vaccinated mothers.

METHODS: Immunogenicity data among children given their first measles vaccine dose between 11 and 22 months of age were pooled from 5 randomized controlled trials conducted in Europe and the United States between 2004 and 2010. Measles antibody titers were measured by enzyme-linked immunosorbent assay before and after each dose; geometric mean concentrations (GMCs) and the proportion seronegative (GMC <150 mIU/mL) were derived by age at first dose.

RESULTS: Among 5542 children given a first measles vaccine dose at 11, 12, 13-14, and 15-22 months of age, the proportion seronegative decreased from 8.5% to 3.2%, 2.4%, and 1.5%, respectively (P < .001), whereas GMCs increased with older age measles vaccine initiation (P < .001). MMRV induced higher GMCs than MMR (P < .001). First and second dose GMCs were highly correlated (Spearman coefficient = 0.8).

CONCLUSIONS: As previously noted among infants born to mothers with history of wild-type measles, antibody responses among children born to vaccinated mothers were reduced based on earlier administration of their first measles vaccine dose at ≤12 vs ≥15 months of age. Negative effects of earlier age at first measles vaccine dose persisted after the second dose. The measles elimination goal may require a careful balance between earlier infant protection and the risk of reduced antibody responses and secondary vaccine failure among successive birth cohorts systematically initiated to measles vaccination <15 months of age.