inclusion criteria: - subjects aged 60 and above with full capacity for civil conduct; - chronic bronchitis (or chronic obstructive pulmonary disease) diagnosed by a medical institution at level i or above; - body temperature < 37.3 ° c confirmed by clinical examination before enrollment ; - able and willing to complete the entire study plan during the study follow-up period; - have the ability to understand the study procedures, voluntarily sign informed consent, and comply with the requirements of the clinical study protocol exclusion criteria for the first dose: - subjects were previously confirmed cases of covid-19 or asymptomatic infected persons; - subjects have history of vaccination against covid-19; - being allergic to any component of vaccines (including excipients) ; - injection of non-specific immunoglobulin within 1 month before enrollment; - injection of live attenuated vaccines within 1 month and injection of other vaccines within 14 days before enrollment; - subjects who have experienced severe allergic reactions to vaccines (e.g. acute anaphylaxis, urticaria, angioneurotic edema, dyspnea, etc.); - having uncontrolled epilepsy and other progressive neurological disorders and a history of guillain-barre syndrome; - having severe liver and kidney diseases, malignant tumors, acute diseases or acute episodes of chronic diseases; - have been diagnosed with congenital or acquired immunodeficiency, hiv infection, lymphoma, leukaemia or other autoimmune diseases; - have been diagnosed with thrombocytopenia or other clotting disorders that may contraindicate subcutaneous injection; - during an acute episode of chronic bronchitis/chronic obstructive pulmonary disease; - other subjects whose physical conditions, as determined by the investigator, are not suitable for inclusion in clinical studies. exclusion criteria for the second dose: - subjects who had vaccine-related adverse reactions after the first dose; - having high fever (axillary temperature ≥39.0℃) for three days after the first dose of inoculation, or severe allergic reaction; - having any adverse nervous system reaction after the first dose; - during the acute onset of a chronic disease, or the recovery of acute complications less than two weeks; - other reasons for exclusion considered by the investigator.

inclusion criteria: - subjects aged 60 and above with full capacity for civil conduct; - chronic bronchitis (or chronic obstructive pulmonary disease) diagnosed by a medical institution at level i or above; - body temperature < 37.3 ° c confirmed by clinical examination before enrollment ; - able and willing to complete the entire study plan during the study follow-up period; - have the ability to understand the study procedures, voluntarily sign informed consent, and comply with the requirements of the clinical study protocol exclusion criteria for the first dose: - subjects were previously confirmed cases of covid-19 or asymptomatic infected persons; - subjects have history of vaccination against covid-19; - being allergic to any component of vaccines (including excipients) ; - injection of non-specific immunoglobulin within 1 month before enrollment; - injection of live attenuated vaccines within 1 month and injection of other vaccines within 14 days before enrollment; - subjects who have experienced severe allergic reactions to vaccines (e.g. acute anaphylaxis, urticaria, angioneurotic edema, dyspnea, etc.); - having uncontrolled epilepsy and other progressive neurological disorders and a history of guillain-barre syndrome; - having severe liver and kidney diseases, malignant tumors, acute diseases or acute episodes of chronic diseases; - have been diagnosed with congenital or acquired immunodeficiency, hiv infection, lymphoma, leukaemia or other autoimmune diseases; - have been diagnosed with thrombocytopenia or other clotting disorders that may contraindicate subcutaneous injection; - during an acute episode of chronic bronchitis/chronic obstructive pulmonary disease; - other subjects whose physical conditions, as determined by the investigator, are not suitable for inclusion in clinical studies. exclusion criteria for the second dose: - subjects who had vaccine-related adverse reactions after the first dose; - having high fever (axillary temperature ≥39.0℃) for three days after the first dose of inoculation, or severe allergic reaction; - having any adverse nervous system reaction after the first dose; - during the acute onset of a chronic disease, or the recovery of acute complications less than two weeks; - other reasons for exclusion considered by the investigator.