Assessed solicited local symptoms were pain, redness and swelling. Any = occurrence of the symptom regardless of intensity. Grade 3 pain = pain that prevented normal activity. Grade 3 redness/swelling = redness/swelling spreading beyond 100 millimeters (mm) injection site.

Assessed solicited general symptoms were chills, gastrointestinal symptoms (including nausea, vomiting, diarrhoea and/or abdominal pain), fatigue, myalgia, headache and fever \[defined Oral cavity or axillary temperature equal to or above (≥) 37.5 degrees Celsius (°C)\]. Any = occurrence of the symptom regardless of intensity grade. Grade 3 symptom = symptom that prevented normal activity. Grade 3 fever = fever ≥ 39.0 °C.

An AE is any untoward medical occurrence in a clinical investigation subject, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. Unsolicited AE is any AE reported in addition to those solicited during the clinical study. Also any 'solicited' symptom with onset outside the specified period of follow-up for solicited symptoms was reported as an unsolicited adverse event.

An SAE is defined as any untoward medical occurrence that resulted in death, was life-threatening, required hospitalization or prolongation of hospitalization, resulted in disability/incapacity in a subject or was a congenital anomaly/birth defect in the offspring of a study subject. AE(s) considered as SAE(s) also include invasive or malignant cancers, intensive treatment in an emergency room or at home for allergic bronchospasm, blood dyscrasias or convulsions that do not result in hospitalization, as per the medical or scientific judgement of the physician.

Potential immune-mediated diseases (pIMDs) are a subset of AEs that include autoimmune diseases and other inflammatory and/or neurologic disorders of interest which may or may not have an autoimmune aetiology.

Efficacy of the investigational vaccine was measured by the rate of moderate and severe AECOPD from 1-month post dose 2 up to study end (i.e. rate expressed per year and calculated as the total number of events over the follow-up exposure time). The CIs of the rate is computed using a model which accounts for repeated events. Anthonisen criteria used to detect potential AECOPD: Worsening of 2 or more of the following major symptoms for at least 2 consecutive days: dyspnoea, sputum volume, sputum purulence, OR Worsening of any major symptom together with any of the following minor symptoms for at least 2 consecutive days: sore throat, cold, fever without other cause, increased cough, increased wheeze. Moderate AECOPD requires treatment with systemic corticosteroids and/ or antibiotics. Severe AECOPD requires hospitalization. Confirmation of any AECOPD was as per investigator's judgement.

Efficacy of the investigational vaccine was measured by the rate of moderate and severe AECOPD from 1-month post dose 2 up to study end (i.e. rate expressed per year and calculated as the total number of events over the follow-up exposure time). The CIs of the rate is computed using a model which accounts for repeated events. Anthonisen criteria used to detect potential AECOPD: Worsening of 2 or more of the following major symptoms for at least 2 consecutive days: dyspnoea, sputum volume, sputum purulence, OR Worsening of any major symptom together with any of the following minor symptoms for at least 2 consecutive days: sore throat, cold, fever without other cause, increased cough, increased wheeze. Moderate AECOPD requires treatment with systemic corticosteroids and/ or antibiotics. Severe AECOPD requires hospitalization. Confirmation of any AECOPD was as per investigator's judgement.