inclusion criteria: male or female <18 years of age. participants will be stratified into different age cohorts (≥12 to < 18 years, ≥5 to < 12 years, ≥2 to < 5 years, and < 2 years of age) based on the age on the day of inclusion. individuals and their legally authorized representative (lar) are willing and able to comply with study requirements, including all scheduled visits, vaccinations, laboratory tests and other study procedures. individuals are willing and able to give an assent (if applicable) and their lars are willing and able to give informed consent on their behalf, prior to screening healthy participants (phase 2 and phase 3) or participants with pre-existing medical conditions who are in a stable medical condition (phase 2) for infants (<1-year-old) - born at full term (gestational age ≥37 weeks) and with a normal birth weight (≥2500 grams). female participants of childbearing potential may be enrolled in the study, if the participant has practiced highly effective contraception for 30 days prior to vaccination, and has a negative pregnancy test on the day of vaccination and has agreed to continue adequate contraception for 3 months after the last vaccination

inclusion criteria: male or female <18 years of age. participants will be stratified into different age cohorts (≥12 to < 18 years, ≥5 to < 12 years, ≥2 to < 5 years, and < 2 years of age) based on the age on the day of inclusion. individuals and their legally authorized representative (lar) are willing and able to comply with study requirements, including all scheduled visits, vaccinations, laboratory tests and other study procedures. individuals are willing and able to give an assent (if applicable) and their lars are willing and able to give informed consent on their behalf, prior to screening healthy participants (phase 2 and phase 3) or participants with pre-existing medical conditions who are in a stable medical condition (phase 2) for infants (<1-year-old) - born at full term (gestational age ≥37 weeks) and with a normal birth weight (≥2500 grams). female participants of childbearing potential may be enrolled in the study, if the participant has practiced highly effective contraception for 30 days prior to vaccination, and has a negative pregnancy test on the day of vaccination and has agreed to continue adequate contraception for 3 months after the last vaccination