A case of COVID-19 meeting the definition for primary efficacy analysis was defined as follows: * Virologically-confirmed case of COVID-19 (of any severity) defined as a positive SARS-CoV-2 specific RT-PCR test in a person with clinically symptomatic COVID-19. * Symptom onset ≥ 15 days after second trial vaccination. * First episode of virologically-confirmed COVID-19, i.e. the participant must not have had a history of virologically-confirmed COVID-19 illness at enrollment or have had developed a case of virologically-confirmed COVID-19 before 15 days after the second trial vaccination. * Participant was SARS-CoV-2 naïve at baseline and Day 43 (defined as seronegative to N protein in the blood samples collected at baseline and Day 43). * Primary efficacy cases were confirmed by an Adjudication Committee. Participants were censored at the first day after unblinding or at the day after receiving the authorized/licensed vaccine, whichever was earlier.

Medically-attended AEs were defined as AEs with medically-attended visits that were 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. Clinic visits for COVID-19 testing resulting in negative test results were not considered as medically attended visits, if there is no confirmed diagnosis and no prescribed concomitant medication. The Investigator assessed the relationship between trial vaccine and occurrence of each AE. Participants were censored at the first day after unblinding or at the day after receiving the authorized/licensed vaccine, whichever was earlier.

An SAE was defined as any untoward medical occurrence that, at any dose: * Resulted in death. * Was life-threatening. * Required inpatient hospitalization or prolongation of existing hospitalization. * Resulted in persistent disability/incapacity. * Was a congenital anomaly/birth defect in the offspring of the participant. * Was an important medical event. The Investigator assessed the relationship between trial vaccine and occurrence of each SAE. Participants were censored at the first day after unblinding or at the day after receiving the authorized/licensed vaccine, whichever was earlier.

An SAE was defined as any untoward medical occurrence that, at any dose: * Resulted in death. * Was life-threatening. * Required inpatient hospitalization or prolongation of existing hospitalization. * Resulted in persistent disability/incapacity. * Was a congenital anomaly/birth defect in the offspring of the participant. * Was an important medical event. The Investigator made an assessment of intensity of each SAE reported during the trial. Each SAE was graded from Mild (Grade 1) to Severe (Grade 3), where higher grades indicated a worse outcome. Participants were censored at the first day after unblinding or at the day after receiving the authorized/licensed vaccine, whichever was earlier.

AESIs included: * AEs with a suspected immune-medicated etiology. * Other AEs relevant to SARS-CoV-2 vaccine development or the target disease. The Investigator assessed the relationship between trial vaccine and occurrence of each AESI. Participants were censored at the first day after unblinding or at the day after receiving the authorized/licensed vaccine, whichever was earlier.

A fatal SAE was defined as an SAE that resulted in death. Participants were censored at the first day after unblinding or at the day after receiving the authorized/licensed vaccine, whichever was earlier.

Solicited local AEs (injection site pain, redness, swelling, and itching) and solicited systemic AEs (fever, headache, fatigue, chills, myalgia, arthralgia, nausea/vomiting, and diarrhea) were recorded on the day of vaccination and the following 7 days using an eDiary. Participants were censored at the first day after unblinding or at the day after receiving the authorized/licensed vaccine, whichever was earlier.

Solicited local AEs (injection site pain, redness, swelling, and itching) and solicited systemic AEs (fever, headache, fatigue, chills, myalgia, arthralgia, nausea/vomiting, and diarrhea) were recorded on the day of vaccination and the following 7 days using an eDiary. The Investigator made an assessment of intensity of each solicited AE reported during the trial. Each solicited AE was graded from Mild (Grade 1) to Severe (Grade 3), where higher grades indicated a worse outcome. Participants were censored at the first day after unblinding or at the day after receiving the authorized/licensed vaccine, whichever was earlier.

Solicited local AEs (injection site pain, redness, swelling, and itching) and solicited systemic AEs (fever, headache, fatigue, chills, myalgia, arthralgia, nausea/vomiting, and diarrhea) were recorded on the day of vaccination and the following 7 days using an eDiary. Duration is calculated as consecutive days with a respective solicited AE regardless of the grade of the AE. AEs ongoing after Day 8 are included. In each case only the longest consecutive duration is displayed. Participants were censored at the first day after unblinding or at the day after receiving the authorized/licensed vaccine, whichever was earlier.

eDiaries were used for collection of unsolicited AEs on each vaccination day and the following 28 days. In addition, participants received a prompt (by e.g., a phone call or text message) to verify whether the participants had any health concerns since the last visit. The Investigator assessed the relationship between trial vaccine and each occurrence of each AE. Participants were censored at the first day after unblinding or at the day after receiving the authorized/licensed vaccine, whichever was earlier.

eDiaries were used for collection of unsolicited AEs on each vaccination day and the following 28 days. In addition, participants received a prompt (by e.g., a phone call or text message) to verify whether the participants had any health concerns since the last visit. The Investigator made an assessment of intensity of each unsolicited AE reported during the trial. Each unsolicited AE was graded from Mild (Grade 1) to Severe (Grade 3), where higher grades indicated a worse outcome. Participants were censored at the first day after unblinding or at the day after receiving the authorized/licensed vaccine, whichever was earlier.

Participants were censored at the first day after unblinding or at the day after receiving the authorized/licensed vaccine, whichever was earlier.