Center for Biologics Evaluation and Research (CBER) criteria for seroprotection rate (SPR) for 18 to 64 years of age is shown if the Lower Limit (LL) of the 99.17% confidence interval (CI) for the SPR meets or exceeds 70%, and for greater than or equal to (≥) 65 years of age if the LL of the 99.17% CI for the SPR meets or exceeds 60%. SPR is defined as the percentage of participants with an HI antibody titer ≥40 1/dilution (DIL). The percentage of participants was calculated along with Clopper-Pearson exact two-sided 99.17% CIs.

CBER criteria for seroconversion rate (SCR) for 18 to 64 years of age is shown if LL of the 99.17% CI for the SCR meets or exceeds 40%, and for ≥65 years of age, if the LL of the 99.17% CI for the SCR meets or exceeds 30%. Seroconversion is defined as a post-vaccination antibody titer ≥40 1/DIL in the serum of participants seronegative before vaccination (i.e. titer \< assay cut-off at Day 1). For seropositive participants (i.e. titer ≥ assay cut-off at Day 1), seroconversion requires a 4-fold rise in post-vaccination HI antibody titer (but at least a titer of 40 1/DIL). The percentage of participants was calculated with Clopper-Pearson exact two-sided 99.17% CIs. Note: The cut-off value for antibody titer was defined by the laboratory before the analysis.

Solicited administered site events assessed were pain, redness and swelling. Any Pain = occurrence of symptom regardless of intensity grade. Any Redness or any Swelling symptom = any symptom having a surface diameter greater than (\>) 20 millimeters (mm).

Solicited systemic events assessed were fatigue, fever, headache, muscle ache all over body, joint pain, shivering, sweating and gastrointestinal symptoms (Nausea, vomiting, diarrhea and abdominal pain). Any = occurrence of symptom regardless of intensity grade. Fever was defined as temperature ≥38 degrees Celsius (°C) for oral route (preferred location for measuring temperature).

An unsolicited adverse event (AE) is an AE that was not solicited using a Participant Diary and that was spontaneously communicated by a participant who had signed the informed consent. Unsolicited AEs include serious and non-serious AEs. Potential unsolicited AEs may have been medically attended (i.e. symptoms or illnesses requiring a hospitalization, or emergency room visit, or visit to/by a health care provider). Unsolicited AEs that were not medically attended nor perceived as a concern by participant were collected during interview with the participants and by review of available medical records at the following visit. An unsolicited adverse event is any event reported in addition to those solicited during the clinical study and any solicited symptom with onset outside the specified period of follow-up for solicited symptoms.

MAEs were defined as adverse events with medically-attended visits that are not routine visits for physical examination or vaccination, such as visits for hospitalization, an emergency room visit, or an otherwise unscheduled visit to or from medical personnel (medical doctor) for any reason.

MAEs were defined as adverse events with medically-attended visits that are not routine visits for physical examination or vaccination, such as visits for hospitalization, an emergency room visit, or an otherwise unscheduled visit to or from medical personnel (medical doctor) for any reason.

A SAE is any untoward medical occurrence that results in death, is life threatening, requires hospitalization or prolongation of existing hospitalization or result in disability/incapacity, is a congenital anomaly/birth defect in the offspring of a study participant. Abnormal pregnancy outcomes were also considered (e.g. spontaneous abortion, fatal death, stillbirth, congenital anomalies, ectopic pregnancy) or other situations where medical or scientific judgement was exercised in deciding whether reporting was appropriate.

pIMDs are a subset of adverse events of special interest that included autoimmune diseases and other inflammatory and/or neurologic disorders of interest which may or may not have had an autoimmune etiology.

pIMDs are a subset of adverse events of special interest that included autoimmune diseases and other inflammatory and/or neurologic disorders of interest which may or may not have had an autoimmune etiology.

A SAE is any untoward medical occurrence that results in death, is life threatening, requires hospitalization or prolongation of existing hospitalization or result in disability/incapacity, is a congenital anomaly/birth defect in the offspring of a study participant. Abnormal pregnancy outcomes were also considered (e.g. spontaneous abortion, fatal death, stillbirth, congenital anomalies, ectopic pregnancy) or other situations where medical or scientific judgement was exercised in deciding whether reporting was appropriate.