Study objectives are to compare

• influenza antibody levels in infant sera and maternal colostrum or breast milk at delivery, 2, and 6 months women who receive influenza immunization in early pregnancy, late pregnancy, or no influenza immunization during pregnancy and their infants

Study hypotheses are that infants born to pregnant women who receive influenza immunization in late pregnancy will have

• higher levels and a longer serum influenza antibody duration in sera (hemagglutination inhibition (HAI) titers) and colostrum/breast milk (influenza-specific IgA and IgG by enzyme-linked immunosorbent assay (ELISA) than infants of women immunized in early pregnancy or not immunized

Inclusion Criteria:

Pregnant women 18-45 years of age from 8-36 weeks gestation in good health as determined by medical history and recent physical exam who

• receive prenatal care at the UUHS Obstetrics and Gynecology Clinics and their infants
• plan to seek care for their infant at the UUHS affiliated Pediatric Clinics (UUHS or SMC Pediatric Clinics)
• plan for their infant to receive influenza immunization at 6 and 7 months of age

Exclusion Criteria:

• maternal history of either a congenital or acquired immunodeficiency including infection (e.g. HIV), chronic steroid use, or malignancy
• serious underlying neurological, cardiac, renal, or pulmonary disease in either the mother or infant
• multiple gestation
• antenatal or postnatal detection at delivery of any major birth defect in the infant
• delivery of the infant before 37 weeks

Pregnant women and their infants receiving care at University of Utah Health Sciences (UUHS) will be recruited and followed.