Could a daily Under-the-Tongue vaccine tame COPD flare-ups?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Written informed consent. * Both sexes. * Age between 35 and 85. * Must be capable of complying with the dosing regimen. * Diagnosis of moderate or severe COPD according to GOLD criteria. * Experienced at least three moderate exacerbations (i.e., those requiring treatment with antibiotics, systemic corticosteroids, or both, as prescribed by their general practitioner or pulmonologist in the standard consultation and/or the Emergency Department of their Clinic) or two exacerbations with at least one requiring hospitalization due to a COPD exacerbation and the other one a moderate exacerbation occurred within the last year. * Not changed their medication for the maintenance treatment of COPD within the past 6 months. * Consumption of 10 or more packs of cigarettes/year. Participants may be or not active smokers. * Live in the Autonomous Community of Madrid throughout the study period. * Women of childbearing age women of must use an approved contraceptive method and obtain a negative result in the urine pregnancy test performed during the screening visit. Exclusion Criteria: * Participants outside allowed age range. * Participants unable to cooperate and/or have a severe psychiatric disorder. * Women who are pregnant, breastfeeding, expect to become pregnant during the study (including assisted reproduction), or who refuse to use contraceptives during the study (including barrier methods). Women who become pregnant during the clinical trial will have to discontinue their participation in it. * Participants who has participated in a study or clinical trial with an investigational product in the last 3 months before inclusion. * Participants diagnosed with asthma based on the guidelines of the American Thoracic Society and the European Respiratory Society. If the investigators are unable to differentiate between COPD and asthma after applying the criteria listed in the following table, a bronchodilator test with inhaled salbutamol must be performed, excluding those subjects with FEV1 changes \>400 ml. * Participants with a diagnosis other than COPD that causes them to have an unstable condition or a life expectancy \<3 years. * Participants who had an exacerbation within 4 weeks before starting the trial. * Participants with moderate COPD who required treatment with inhaled corticosteroids in the last 4 weeks. * Participants with moderate COPD who received systemic corticosteroids (orally, intramuscularly, or intravenously) in the last 4 weeks. * Participants diagnosed with a Primary or Secondary Immunodeficiency within the 12 months preceding their inclusion in the clinical trial or the trial's baseline visit. * Participants diagnosed with chronic lymphoproliferative disease. * Participants diagnosed with chronic infectious disease. * Participants with chronic heart disease, arrhythmias, or episodes of arrhythmia secondary to the administration of bronchodilators. * Participants diagnosed with COPD and chronic colonization by Pseudomonas aeruginosa. * Participants with COPD and bronchiectasis diagnosed by CT imaging before the age of 40. * Participants diagnosed with very severe COPD according to the GOLD classification. * Participants requiring home oxygen therapy or non-invasive mechanical ventilation. * Participants with a history of hypersensitivity to any of the vaccine's components. * Participants receiving immunosuppressive treatment with: azathioprine, methotrexate, ciclosporin, cyclophosphamide, tacrolimus, antimalarial drugs, or gold salts. * Participants who have been treated with monoclonal antibodies such as rituximab or TNF-alpha inhibitors in the last 6 months. * Participants receiving chronic treatment with azithromycin or inhaled antibiotics (tobramycin or colistin).