Respiratory Syncytial Virus (RSV) is the number one cause of hospitalizations and death for severe respiratory infections in young infants across the world. Antibodies made by our immune system are important to help fight viruses like RSV. Newborns lack their own antibodies at birth and rather obtain them from their mothers during pregnancy. To increase antibody levels at birth in babies, researchers have proposed to vaccinate mothers against RSV during pregnancy. We do not completely understand how much antibodies are critical for protection against RSV infection in early life. We also do not know which function(s) of RSV antibodies are associated with protection from RSV disease in young infants. Infants’ samples obtained at delivery will be tested for levels and different functions of RSV antibodies and this will be correlated with the risk of infection in infants. Data from these projects will inform RSV vaccine design and development, especially in pregnancy as the levels and functions of RSV antibodies after vaccination should be similar to the levels and functions that protects from RSV disease.