inclusion criteria: - subjects aged ≥18. - body temperature < 37.3 ° c confirmed by clinical examination before enrollment . - subjects who meet the diagnostic criteria for hiv infection and aids. - cd4+ count is less than 500/ul and more than 50/ul . - female subjects of reproductive age declare that they are not pregnant, have no birth plan in the first 3 months after enrollment, and have taken effective contraceptive measures in the first 2 weeks 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. - subjects participating in the past clinical trial have completed two doses of covid-19 vaccine and blood collection before and after immunization;

inclusion criteria: - subjects aged ≥18. - body temperature < 37.3 ° c confirmed by clinical examination before enrollment . - subjects who meet the diagnostic criteria for hiv infection and aids. - cd4+ count is less than 500/ul and more than 50/ul . - female subjects of reproductive age declare that they are not pregnant, have no birth plan in the first 3 months after enrollment, and have taken effective contraceptive measures in the first 2 weeks 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. - subjects participating in the past clinical trial have completed two doses of covid-19 vaccine and blood collection before and after immunization;