Background: To evaluate the immunogenicity and safety of the COVID-19 vaccine (Vero cell), inactivated, in a population aged ≥60 years with hypertension or(/and) diabetes mellitus. Methods: A total of 1440 participants were enrolled and divided into four groups, 330 in the hypertension group, 330 in the diabetes group, 300 in the hypertensive combined with diabetes group (combined disease group), and 480 in the healthy population group. Two doses of the COVID-19 vaccine (Vero cell), inactivated, were administered at a 21-day interval and blood samples were collected before vaccination and 28 days after the second dose to evaluate the immunogenicity. The adverse events and changes in blood pressure and blood glucose levels after vaccination were recorded. Results: The seroconversion rate of the COVID-19 neutralizing antibodies was 100% for all participants. The post-inoculation geometric mean titer (GMT) in the four groups of the hypertension, diabetes, combined disease, and healthy populations were 73.41, 69.93, 73.84, and 74.86, respectively. The seroconversion rates and post-vaccination GMT in the hypertension, diabetes, and combined disease groups were non-inferior to the healthy population group. The rates of vaccine-related adverse reactions were 11.93%, 14.29%, 12.50%, and 9.38%, respectively. No serious adverse events were reported during the study. No apparent abnormal fluctuations in blood pressure and blood glucose values were observed after vaccination in participants with hypertension or(/and) diabetes. Conclusions: The COVID-19 vaccine (Vero cell), inactivated, showed good immunogenicity and safety in patients aged ≥60 years suffering from hypertension or(/and) diabetes mellitus.

Importance: The protective efficacy of COVID-19 vaccinations has declined over time such that booster doses are required. Objective: To evaluate the efficacy and adverse events of booster doses of two inactivated COVID-19 vaccines. Design: This is a double-blind, randomized, placebo-controlled phase 3 trial aiming to evaluate the protective efficacy, safety, and immunogenicity of inactivated SARS-CoV-2 vaccine (Vero cells) after inoculation with booster doses of inactivated COVID-19 vaccine. Setting: Healthy volunteers were recruited in an earlier phase 3 trial of two doses of inactivated vaccine. The participants in Abu Dhabi maintained the blind state of the trial and received a booster dose of vaccine or placebo at least six months after the primary immunization. Participants: Adults aged 18 and older with no history of SARS-CoV, SARS-CoV-2, or Middle East respiratory syndrome infection (via onsite inquiry) were screened for eligibility. Interventions: A total of 9370 volunteers were screened and randomly allocated, of which 61 voluntarily withdrew from the screening stage without booster inoculation; 9309 received the booster vaccination, with 3083 in the WIV04 group, 3150 in the HB02 group, and 3076 in the alum-only group. Further, 5μg and 4μg of inactivated SARS-CoV-2 virion was adsorbed into aluminum hydroxide in a 0.5 mL aqueous suspension for WIV04 and HB02 vaccines. Main Outcomes and Measures: The primary efficacy outcome was the prevention of PCR-confirmed symptomatic COVID-19 from 14 days after the booster vaccine in the per-protocol population. A safety analysis was performed in the intention-to-treat population. Results: Symptomatic COVID-19 was identified in 36 participants in the WIV04 group (9.9 [95% CI, 7.2–13.8] per 1000 person-years), 28 in the HB02 group (7.6 [95% CI, 5.2–11.0] per 1000 person-years), and 193 in the alum-only group (55.2 [95% CI, 47.9–63.5] per 1000 person-years), resulting in a vaccine efficacy of 82.0% (95% CI, 74.2–87.8%) for WIV04 and 86.3% (95% CI, 79.6–91.1%) for HB02. One severe case of COVID-19 occurred in the alum-only group, and none occurred in the vaccine groups. Adverse reactions within seven days after vaccination occurred in 29.4% to 34.3% of participants in the three groups. Serious adverse events were rare and not related to vaccines (WIV04: 17 [0.5%]; HB02: 11 [0.4%]; alum only: 40 [1.3%]). Conclusions and Relevance: This study evaluated the safety of the booster dose, which was well tolerated by participants. Booster doses given over six months after the completion of primary immunization can help to provide more-effective protection against COVID-19 in healthy people 18 years of age or older. At the same time, the anti-SARS-CoV-2 antibodies produced by the two groups of experimental vaccines exhibited extensive cross-neutralization against representative SARS-CoV-2 variants. Trial Registration: This study is registered on ClinicalTrials.gov (NCT04510207).