A Phase 3, Randomized, Observer-blind, Active-controlled, Case-driven Study to Investigate the Safety, Efficacy, and Immunogenicity of mRNA-1010 Candidate Seasonal Influenza Vaccine Compared With a Licensed Inactivated Seasonal Influenza Vaccine in Adults ≥50 Years of Age

Number of Participants with Solicited Local and Systemic Adverse Reactions (ARs)

时间窗: Day 1 to Day 7

Number of Participants with Unsolicited Adverse Events (AEs)

时间窗: Day 1 to Day 28

Number of Participants with Medically Attended AEs (MAAEs), AEs Leading to Discontinuation, Serious Adverse Events (SAEs), or Adverse Events of Special Interest (AESI)

时间窗: Day 1 to Day 181

Time to First Episode of RT-PCR Confirmed Protocol Defined ILI

时间窗: Day 14 up to End of Season (up to approximately Day 181)

ILI caused by any influenza A or B strains.

Number of Participants With Solicited Local and Systemic Adverse Reactions (ARs)

时间窗: Day 1 up to Day 7

Solicited ARs were recorded daily using electronic diaries (eDiaries). Local ARs: injection site pain, erythema (redness), swelling/induration (hardness); and axillary (underarm) swelling or tenderness ipsilateral to the side of injection. Systemic ARs: fever, headache, fatigue, myalgia, arthralgia, nausea/vomiting, and chills. Note, not all solicited ARs were considered adverse events (AEs). Investigator reviewed whether the solicited AR was also to be recorded as an AE. A summary of all Serious Adverse Events (SAEs) and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

Number of Participants With Unsolicited Adverse Events (AEs)

时间窗: Day 1 up to Day 28

An unsolicited AE was defined as any AE reported by the participant that was not specified as a solicited AR in the protocol. An AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. A summary of all SAEs and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

Number of Participants With Medically Attended AEs (MAAEs), AEs Leading to Study Discontinuation, SAEs, or Adverse Events of Special Interests (AESIs)

时间窗: Day 1 up to Day 181

MAAEs were AEs that led to an unscheduled visit to a healthcare provider. SAEs were AEs that resulted in death, were life threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant incapacity or substantial disruption of the ability to conduct normal life functions, a congenital anomaly or birth defect, or was a medically important event. AESIs were AEs (serious or nonserious) of scientific and medical concern specific to the Sponsor's product or program for which ongoing monitoring and immediate notification by the investigator to the Sponsor was required. A summary of all SAEs and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

Number of Participants With First Episode of Reverse Tanscription Polymerase Chain Reaction (RT-PCR) Confirmed Protocol Defined Influenza-like Illness (ILI) Caused by Any Influenza A or B Strains

时间窗: Day 14 up to end of influenza season (up to 7.5 months)

Protocol-defined ILI: At least 1 systemic symptom (temperature \>37.2 degrees celsius \[°C\] \[\>99.0 degrees Fahrenheit {°F}\], chills, feverish, tiredness, headaches, or myalgia) and at least 1 respiratory symptom (sore throat, cough, sputum production, wheezing, or difficulty breathing).