Safety and Immunogenicity of mRNA-1653, a Combined Human Metapneumovirus (hMPV) and Parainfluenza Virus Type 3 (PIV3) Vaccine, in Healthy Adults, and Children 12 to 59 Months of Age With Serologic Evidence of Prior Exposure

This clinical study will assess the safety and immunogenicity of 2 dose levels of mRNA-1653, a combined human metapneumovirus and human parainfluenza virus type 3 vaccine, in healthy adults (18 to 49 years of age) and 2 dose levels in children (12 to 59 months of age) with serologic evidence of prior exposure. The safety profile of the adult cohort will permit enrollment of the pediatric cohort.