Wegrã³w, Poland

A Study to Evaluate the Safety and Immunogenicity of the mRNA COVID-19 Vaccines in Healthy Children Between 6 Months to Less Than 6 Years of Age

Part 1 will enroll participants aged 6 months to <6 years who have not been previously vaccinated against SARS-CoV-2. Participants will receive 2 doses of the mRNA-1273.214 vaccine. Part 2 will enroll participants aged 6 months to <6 years who have previously been vaccinated with a mRNA-1273 primary series in Study mRNA-1273-P204 (NCT04796896). Participants will receive a single BD of the mRNA-1273.214 vaccine, at least 4 months after completion of the mRNA-1273 primary series. Part 3 will enroll participants aged 6 months to <6 years who have previously been vaccinated with an authorized/approved COVID-19 vaccine. Participants will receive a BD of the mRNA-1273.815 vaccine at least 4 months after the last receipt of a COVID-19 vaccine. Part 4 will evaluate mRNA-1273.815 vaccine administered as a single dose to SARS-CoV-2 vaccine-naïve participants aged 2 years to <5 years of age enrolled in Cohort A (Part 4A), compared to 2 doses given to SARS-CoV-2 vaccine-naïve participants aged 6 months to <2 years enrolled in Cohort B (Part 4B).