Participant disposition by study part.
infection
INFECTION, ADVERSE EVENT, CARDIAC ARREST, INFLUENZA
One participant in the mRNA-1010 100-µg group in Part 2 of the study died due to cardiac arrest. This adverse event was considered by the investigator as unrelated to the study vaccination. All randomly assigned participants who received study vaccination were included in the safety population; participants were included in the group based on the actual vaccine received. The immunogenicity per-protocol population included all randomly assigned participants who received vaccination and complied with immunogenicity blood sampling timing to have baseline and ≥1 post-vaccination time point assessment, did not have influenza infection at baseline through Day 29 (as documented by polymerase chain reaction), and had no major protocol deviation that impacted the immune response. mRNA messenger RNA. *There was 1 dosing error in Part 1 (In Part 2 of the trial, a total of 501 participants aged ≥18 years were randomly assigned to receive a single dose of Afluria (