Maternal measles antibodies and infant susceptibility in Chandigarh, India

Abstract

Background: Measles continues to be endemically transmitted in many parts of the world including India. The single dose measles vaccine was first introduced in India in 1985 with recommendation for a second dose added in 2010. Consequently, most mothers and women of reproductive age in India have not received the two recommended doses of vaccine. This study seeks to understand the impact of the changing dynamic of natural measles infection versus vaccination on maternal and infant measles antibody levels. We compare antibodies in infants and their mothers at the time of the birth of their child and through the infant's first year of life. Methods & Materials: Pregnant mothers were systematically selected into this population-based cohort study in Chandigarh, India. Serum samples were tested for anti-measles IgG antibodies from mothers at the time of their infant's birth, and from infants at birth, 3, 6, 9, and 12 months. A positive measles reading (indicating immunity and protection from subsequent infection) was defined as > 12 U/ml. The study is ongoing. Results: Of the 306 mother-infant dyads enrolled in the study, the mean maternal IgG titer of infants who were IgG positive was 97.0 U/ml (SD ± 65.0) and the mean maternal IgG titer of infants who were IgG negative was 18.7 U/ml (SD ± 29.5). Mean antibody tiers in mothers were also higher for mothers whose infants tested IgG positive at three months, 142.8 U/ml (SD ± 60.1), compared to those testing IgG negative 65.7 U/ml (SD ± 56.6). Infant antibody titers at birth were significantly greater among infants whose mothers had reported measles infection 145.6 U/ml (SD ± 72.4) than among mothers who were vaccinated 102.1 U/ml (SD ± 63.2) (P = 0.01). Conclusion: Greater measles antibody titers in mothers resulted in infants retaining immunity at birth and at 3 months. Moreover, mothers who previously had disease gave birth to infants with higher titers than infants born to vaccinated mothers. Programs targeting vaccination of young adult women of reproductive age could bolster population level immunity and also enable mothers to pass on higher levels of protective antibodies to their infants.