Study of the Infectivity, Safety and Immunogenicity of Two Recombinant, Live-Attenuated, B/HPIV3 Vectored Vaccines Expressing the Fusion Glycoprotein of HMPV Delivered by Nasal Spray to HPIV3-Seropositive Children 24 to <60 Months of Age

B/HPIV3/HMPV-PreF-A is a live-attenuated vaccine candidate. The B/HPIV3/HMPV-PreF-A vaccine is provided in a sterile 2.0-mL cryovial, each containing 0.6 mL of vaccine with a titer of approximately 10\^6.7 PFU/mL. The vaccine virus concentrate is diluted with Lactated Ringer's Solution for Injection to a dose of approximately 10\^5.6 PFU in a 0.2 mL volume.

B/HPIV3/HMPV-F-B365 is a live-attenuated vaccine candidate. The B/HPIV3/HMPV-F-B365 vaccine is provided in a sterile 2.0-mL cryovial, each containing 0.6 mL of vaccine with a titer of approximately 10\^6.3 PFU/mL. The vaccine virus concentrate is diluted with Lactated Ringer's Solution for Injection to a dose of approximately 10\^5.6 PFU in a 0.2 mL volume.

Lactated Ringer's Injection, USP is a sterile, nonpyrogenic solution for fluid and electrolyte replenishment. It will be drawn up in a sterile syringe to a volume of 0.2 mL.