CoronaVac

The candidate vaccine elicited immune responses in mice, rats and non-human primates. It was safe and protected rhesus macaques in viral challenges. Antibody-dependent enhancement was not observed.

The vaccine was well tolerated and induced humoral responses against SARS-CoV-2. The immunogenicity was moderate. An improvement in vaccine manufacturing process resulted in increase of seroconversion rates over 90% in both 3 μg and 6 μg dose groups. This was likely due to higher abundance of intact SARS-CoV-2 spike protein in the improved formulation. The 3 μg dose was suggested for phase III clinical trials. Sample size: "Days 0 and 14" pooled vaccination cohorts: 144 (3 μg group) + 144 (6 μg group) + 84 placebo; "Days 0 and 28" pooled vaccination cohorts: 144 (3 μg group) + 144 (6 μg group) + 83 placebo. Dosage: 3 or 6 μg on days 0 and 14 or 0 and 28. Endpoints: The seroconversion of neutralising antibodies to live SARS-CoV-2 (primary immunogenic endpoint); adverse reactions (primary safety endpoint).

No severe adverse reactions linked to the vaccine were observed. Phase I: seroconversion was observed in 100% and 95.7% of subjects in the 3 μg and the 6 μg group, respectively. Phase II: seroconversion was observed in 90.7%, 98%, and 99% of subjects in the 1.5 μg, the 3 μg and the 6 μg group, respectively. The data support the use of the 3 μg dose in the elderly subjects in phase III trials. Sample size: Phase I (per-protocol analyses): 24 + 12 placebo (3 μg group), 23 + 12 placebo (6 μg group); phase II (per-protocol analyses):  97 (1.5 μg group) + 98 (3 μg group) + 98 (6 μg group) + 47 placebo. Dosage: Phase I: two doses (either 3 μg each or 6 μg each) of inactivated virus in alum solution, 28 days apart; phase II: two doses (either 1.5 μg each, 3 μg each, or 6 μg each) of inactivated virus in alum solution, 28 days apart. Primary endpoints: safety - adverse reactions within 28 days of injection; immunogenicity - seroconversion at day 28 post second dose.