The overall objective of the project is to identify the determinants of antibody-mediated immunity in infants born to mothers immunized during pregnancy. Using maternal pertussis immunization as a model, the project will identify key predictors and potential determinants of vaccine responses in pregnant women, of the transfer of maternal antibodies to the newborn and of vaccine responses in infants. A systems biology approach will be used to delineate pre-vaccination and post-vaccination cellular and molecular correlates of the immune response to pertussis immunization in peripheral blood and in breastmilk.