Due to limited data available on the safety and immune response to live attenuated influenza vaccine (LAIV) in breast-feeding women and the lack of information on the induction of immunoglobulin (Ig) A and IgG against influenza virus in breast milk, this study compares the safety in mothers and their infants and immunogenicity in mothers of standard dose inactivated trivalent influenza vaccine (TIV) and LAIV when administered between 28-120 days of delivery in breastfeeding women. This is a multi-site, randomized, double-blinded trial in 240 post-partum breastfeeding women, 18-49 years of age and their infants. Once enrolled, a blood sample and a breast milk sample will be collected. Nasal swabs will be obtained and targeted physical examinations (TPE) will be conducted from mother and infant, if indicated. Each subject will receive either a single intramuscular (IM) 0.5 milliliter (mL) dose of TIV and 0.2 mL of placebo administered intranasally, or 0.2 mL intranasal dose of LAIV and 0.5 mL of placebo administered IM. All subjects will maintain a memory aid recording oral temperature, and systemic and local adverse events (AEs) for 8 days after study products have been administered. Approximately day 2 and 8 all subjects will return to the clinic for collection of breast milk samples and nasal swabs (mother and infant) and the memory aid will be reviewed. Approximately Day 28 after vaccination, all subjects will return to the clinic for breast milk and a blood sampling. During the time between vaccination and the day 28 visit, if mother or infant has an influenza-like illness (ILI), a clinic visit may be required within 72 hours of illness onset. The clinic visit will be required for any illness that meets the Centers for Disease Control and Prevention's definition of an ILI for the mother. Investigator discretion will discern if an illness in the infant requires an ILI visit. Any respiratory or gastrointestinal (GI) serious adverse event (SAE) in the infant will also require a clinic visit. If the mother has an ILI, nasal swabs will be collected on her, and samples from the infant (if possible). If the infant has an ILI, nasal swabs will be collected on both the mother and infant. At approximately Day 42 after vaccination, all subjects will have a phone call for assessment of any medically attended GI or respiratory illness in the infant from Day 29-42. Approximately 6 months after vaccination all subjects will have a phone call for assessment of any SAEs in the subject or the infant since Day 42. SAE data and new onset chronic medical conditions in the mother will be collected from Day 0-180. At all study visits, subjects will be asked about acute, temporary breast diseases (mastitis, abscesses) and any changes in breastfeeding, i.e., interruption and if so, how long (in weeks). Subjects will report information on current breast milk consumption by infant. Unsolicited non-serious AE data will be captured Day 0-28. Respiratory and GI AEs will be captured for the infant from Day 28-42. SAE data will be captured from Day 0-180 for both mother and infant. Blood samples will be tested for hemagglutination inhibition (HAI), IgG, and IgA as measured by enzyme linked-immunosorbent assay (ELISA). Breast milk samples will be assayed for IgA and IgG antibodies by ELISA. Breast milk and nasal swabs will also be tested for LAIV. Parent protocol to sub-study 11-0048.