• Number of all-cause moderate and severe AECOPD per subjects [ Time Frame: Up to Month 12 ]
  Number of all-cause moderate and severe AECOPD per subjects will be analyzed at given time point.
• Incidences of all-cause moderate and severe AECOPD per subject [ Time Frame: Up to Month 12 ]
  Incidences of all-cause moderate and severe AECOPD per subject will be assessed.
• Number of subjects with first evaluable and adjudicated moderate or severe AECOPD that have infectious or non-infectious etiology [ Time Frame: Up to Month 12 ]
  Number of subjects with first evaluable and adjudicated moderate or severe AECOPD that have infectious or non-infectious etiology will be analyzed at given time point.
• Microbiome composition of sputum in stable-state COPD [ Time Frame: Baseline and at Month 12 ]
  Sputum samples will be collected at given time point to assess microbiome composition of sputum in stable-state COPD subjects and measure by bacterial ribosomal ribonucleic acid (rRNA) sequencing.
• Microbiome composition of sputum during subject's first evaluable moderate or severe AECOPD [ Time Frame: Up to Month 12 ]
  Sputum samples will be collected to assess microbiome composition of sputum during subject's first evaluable moderate or severe AECOPD and measured by bacterial ribosomal ribonucleic acid (rRNA)sequencing.
• Number of subjects with first evaluable sputum samples that are positive for potentially pathogenic viruses in stable state COPD [ Time Frame: Baseline and at Month 12 ]
  Sputum samples will be collected at given time point and will be analyzed by Quantitative polymerase chain reaction (qPCR).
• Number of subjects with first evaluable sputum samples that are positive for potentially pathogenic viruses during subject's first evaluable moderate or severe AECOPD [ Time Frame: Up to Month 12 ]
  Sputum samples will be collected at given time point and will be analyzed by qPCR.
• Number of subjects with first evaluable sputum samples that are positive for potentially pathogenic bacteria in stable state COPD [ Time Frame: Baseline and at Month 12 ]
  Sputum samples will be collected at given time point and will be analyzed by bacterial culture or qPCR.
• Number of subjects with first evaluable sputum samples that are positive for potentially pathogenic bacteria during subject's first evaluable moderate or severe AECOPD [ Time Frame: Up to Month 12 ]
  Sputum samples will be collected at given time point and will be analyzed by bacterial culture or qPCR.
• Number of EXACT events per subject over the course of 12 months [ Time Frame: Up to Month 12 ]
  An EXACT event is defined as an increase in EXACT score more than or equal to 12 points for 2 days or more than or equal to 9 points for 3 days, above the subject's mean Baseline. Number of EXACT events per subject will be assessed.
• Incidence of EXACT events per subject over the course of 12 months [ Time Frame: Up to Month 12 ]
  Incidences of EXACT events per subject will be assessed.
• Number of AECOPD events [ Time Frame: Up to Month 12 ]
  Number of AECOPD event will be analyzed.
• Severity of AECOPD according to healthcare utilization [ Time Frame: Up to Month 12 ]
  Severity of AECOPD will be analyzed at given time point according to healthcare resource utilization.
• Severity of EXACT events [ Time Frame: Up to Month 12 ]
  Severity of EXACT events will be analyzed according to EXACT total score at given time point.
• Duration of AECOPD [ Time Frame: Up to Month 12 ]
  Duration of AECOPD will be analyzed at the given time point.
• Duration of EXACT events [ Time Frame: Up to Month 12 ]
  Duration of EXACT events will be analyzed according to the EXACT total score at given time point.
• Mean change in CAT score [ Time Frame: Baseline and up to Month 12 ]
  The CAT is a 8-item, subject-completed instrument that covers symptoms such as cough, phlegm, chest tightness and breathlessness, and disease impacts including physical activity, confidence, sleep and energy. Subjects will be asked to score each item on a scale ranging from 0 (no symptom or impact at all) to 5 (maximal symptom or impact). Mean change in CAT score between stable-state COPD, and during and following subject's first evaluable moderate or severe AECOPD will be assessed.
• Mean change in CAT score over the course of 12 months [ Time Frame: Baseline and up to Month 12 ]
  The CAT is a 8-item, subject-completed instrument that covers symptoms such as cough, phlegm, chest tightness and breathlessness, and disease impacts including physical activity, confidence, sleep and energy. Subjects will be asked to score each item on a scale ranging from 0 (no symptom or impact at all) to 5 (maximal symptom or impact). Mean change in CAT score over the course of 12 months will be assessed.
• Mean change in EXACT score [ Time Frame: Baseline and up to Month 12 ]
  EXACT is a validated, self-administered, 14-item daily diary that assesses 11 respiratory symptoms and 3 additional symptoms, which together characterize COPD exacerbations. The EXACT total score will range from 0 to 100, with higher scores indicating a more severe condition. Mean change in EXACT score between stable-state COPD, and subject's first evaluable moderate or severe AECOPD will be assessed.
• Mean change in Evaluating Respiratory Symptoms (E-RS) COPD total score [ Time Frame: Baseline and up to Month 12 ]
  The E-RS: COPD comprises 11 of the 14 items of the parent EXACT that are specifically related to respiratory symptoms and will be completed using the eDiary. The RS-Total score is computed by taking the sum of the items comprising the instrument, with scores ranging from 0 to 40, with higher scores indicating more severe respiratory symptoms. Mean change in E-RS: COPD total score between stable-state COPD, and subject's first evaluable moderate or severe AECOPD will be assessed.
• Mean change in E-RS: COPD subscale scores [ Time Frame: Baseline and up to Month 12 ]
  The three subscales of E-RS: COPD score are RS-Breathlessness (0-17), RS-Cough & Sputum (0-11), and the RS-Chest Symptoms (0-12) scores scale with higher scores indicating more severe respiratory symptoms. Mean change in E-RS: COPD subscale scores between stable-state COPD, and subject's first evaluable moderate or severe AECOPD will be assessed.
• Mean change in E-RS: COPD total scores over the course of 12 months [ Time Frame: Baseline and up to Month 12 ]
  The three subscales of E-RS: COPD score are RS-Breathlessness, RS-Cough & Sputum, and the RS-Chest Symptoms scores scale. Total of the subscale will range from 0 to 40, with higher scores indicating more severe respiratory symptoms.
• Mean change in E-RS: COPD subscale scores over the course of 12 months [ Time Frame: Baseline and up to Month 12 ]
  The three subscales of E-RS: COPD score are RS-Breathlessness (0-17), RS-Cough & Sputum (0-11), and the RS-Chest Symptoms (0-12) scores scale with higher scores indicating more severe respiratory symptoms.
• Mean change in Forced expiratory volume in 1 second (FEV1) [ Time Frame: Baseline and up to Month 12 ]
  FEV1 is the volume of air that can be forced out in one second after taking a deep breath. Mean change in FEV1 between stable-state COPD, during subject's first evaluable moderate or severe AECOPD, and at Month 12.
• Mean rate of AECOPD related healthcare resource utilization per subject [ Time Frame: Up to Month 12 ]
  Mean rate of AECOPD related related healthcare resource utilization per subject will be analyzed at given time point.
• Mean rate of non-AECOPD related healthcare resource utilization per subject [ Time Frame: Up to Month 12 ]
  Mean rate of non-AECOPD related healthcare resource utilization per subject will be analyzed at given time point.
• Annual rate of AECOPD related healthcare resource utilization per subject [ Time Frame: Up to Month 12 ]
  Annual rate of AECOPD related healthcare resource utilization will be analyzed at given time point.
• Annual rate of non-AECOPD related healthcare resource utilization per subject [ Time Frame: Up to Month 12 ]
  Annual rate of non-AECOPD related healthcare resource utilization will be analyzed at given time point.

• Other: Modified American Thoracic Society and National Heart and Lung Institute-Division of Lung Disease Respiratory (Mod. ATS-DLD-078)
  The medical, family, smoking and occupational history of subjects will be assessed using Mod. ATS-DLD-078 questionnaire. It will be used to collect the subject's history of selected respiratory symptoms and respiratory events as well as key comorbidities.
• Other: Modified Medical Research Council (mMRC) Dyspnea Scale
  The severity of dyspnea attributable to respiratory diseases including COPD will be assessed using a 5-point mMRC dyspnea scale ranging from 0 (breathless only with strenuous exercise) to 4 (too breathless to leave the house).
• Other: Exacerbations of Chronic Pulmonary Disease Tool (EXACT)
  EXACT is a validated, self-administered, 14-item daily diary that assesses 11 respiratory symptoms and 3 additional symptoms, which together characterize COPD exacerbations. This will be completed by subjects daily using their electronic diary (eDiary). The EXACT total score will range from 0 to 100, with higher scores indicating a more severe condition.
• Other: COPD Assessment Test (CAT)
  The CAT is a validated measure of health status in COPD. It is an 8-item, subject-completed instrument that covers symptoms such as cough, phlegm, chest tightness and breathlessness, and disease impacts including physical activity, confidence, sleep and energy. Subjects will be asked to score each item on a scale ranging from 0 (no symptom or impact at all) to 5 (maximal symptom or impact).
• Other: Evaluating Respiratory Symptoms in COPD (E-RS: COPD)
  The E-RS: COPD comprises 11 of the 14 items of the parent EXACT that are specifically related to respiratory symptoms and will be completed using the eDiary. The RS-Total score is computed by taking the sum of the items comprising the instrument, with scores ranging from 0 to 40, with higher scores indicating more severe respiratory symptoms.
• Other: Telephonic interviews
  During the telephonic interviews, the potential AECOPD will be confirmed according to the AECOPD criteria, and if confirmed, the severity will be assessed according to healthcare utilization as mild, moderate or severe.
• Other: Electronic Diary (eDiary)
  Subjects will be asked to complete their eDiary every evening before bedtime. The eDiary consists of a total of 20 questions, which include screening questions for the detection of AECOPD during the study and the EXACT.
• Diagnostic Test: Chest X-ray
  A chest x-ray will be used at Screening visit to assess the subject's eligibility to participate in the study. A local radiologist will review the x-ray and notify the investigator of any abnormalities not considered to be caused by COPD.
• Diagnostic Test: Spirometry
  Spirometry measurements will be obtained using spirometry equipment. At least 3 acceptable spirometry efforts (with no more than 8 attempts) will be obtained.
• Other: Sputum Sampling
  Sputum samples will be collected from the subjects and will be analyzed for the presence and quantity of specific cell types and biomarkers to investigate the etiology of the AECOPD.
• Other: Blood sampling
  Blood samples will be collected from the subjects during the study and will be analyzed for the concentration of biomarkers to investigate the etiology of the AECOPD.

Inclusion Criteria:

• Subjects must be able and willing to comply with the requirements of the protocol.
• Subject must be aged greater than or equal to 40 years at the time of signing the informed consent form (ICF).
• Subjects must have a record of a clinical diagnosis of COPD, ACOS or CB.
• Subjects must have moderate to severe airflow limitation based on spirometry:FEV1 percent predicted normal greater than or equal to 40 to less than or equal to 80% and post-bronchodilator FEV1/forced vital capacity (FVC) ratio less than 0.7.
• Subjects must be symptomatic, defined as having a CAT score greater than or equal to 10.
• Subjects must have a documented history of at least 1 LRTI treated with antibiotics and/or oral/systemic corticosteroids, which may include an exacerbation of COPD, in the 12 months prior to Screening, and must have not experienced either of these in the 4 weeks prior to Screening, and must be determined to be stable-COPD by the investigator.
• Subjects must be current or former tobacco (cigarette) smokers with a smoking history of greater than or equal to 10 pack-years.
• Subjects may be male or female.
• For female subjects: A female subject is eligible to participate if she is not pregnant or breastfeeding, and at least one of the following conditions applies: Is not a woman of child bearing potential (WOCBP) or Is a WOCBP and using an acceptable contraceptive method during the study period.The investigator should evaluate the effectiveness of the contraceptive method. A WOCBP must have had a highly sensitive urine pregnancy test within 2 weeks prior to enrolment that proved negative. If a urine pregnancy test cannot be confirmed as negative (example given [e.g.], an ambiguous result), a serum pregnancy test is required. In such cases, the subject must be excluded from participation if the serum pregnancy result is positive. The investigator is responsible for review of subject's medical history, menstrual history, and recent sexual activity to decrease the risk of including a woman with an early undetected pregnancy.
• Subjects must be capable of giving signed informed consent.

Exclusion Criteria:

• Subjects with a diagnosed respiratory disorder other than COPD, ACOS or CB (such as: sarcoidosis; active tuberculosis or are receiving tuberculosis treatment; clinically significant bronchiectasis (greater than 20% lung damage on computed tomography [CT] scan), lung fibrosis, pulmonary embolism, or pneumothorax; lung cancer diagnosed within the previous 5 years; asthma only or a current primary diagnosis of asthma in the opinion of the investigator); or chest imaging revealing evidence of clinically significant abnormalities not believed to be due to the presence of COPD.
• Subjects with a diagnosis of alpha-1 antitrypsin deficiency as the underlying cause of COPD.
• Subjects who have had lung surgery within 12 months prior to Screening, or plans to have lung surgery within 12 months after study entry.
• Subjects with any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination (no laboratory testing required).
• Subjects who have a psychiatric disorder or any other condition that interferes with the ability to understand the study procedures.
• Subjects who have received antibiotics within 1 month of Screening or have received antibiotics for more than 30 days within 90 days prior to Screening.
• Subjects who have received systemic corticosteroids (oral/intravenous/intramuscular) for more than 14 consecutive days within 90 days prior to giving informed consent.
• Subjects who have received macrolides for more than 30 days within 90 days prior to Screening.
• Subjects who have received chemotherapy for cancer in the 12 months prior to Screening.
• Participation in the study would result in loss of blood or blood products in excess of 500 milliliter (mL) within 12 months.
• Subjects who have participated in a clinical study and been exposed to an investigational vaccine, pharmaceutical product or device within 30 days prior to Screening, or within five half-lives (t1/2) or twice the duration of the biological effect of the investigational product (whichever is longer).
• Subjects who are unable to perform spirometry due to, for example, recent eye surgery or thoracic or abdominal surgery, unstable cardiovascular status, recent myocardial infarction or pulmonary embolism or an allergy to short-acting beta2-agonsts (SABAs).
• Subjects who are unable to use or to comply with daily completion of the eDiary.