Tianjin, March 14, 2022 – CanSino Biologics Inc. (“CanSinoBIO”) (SSE: 688185, HKEX: 06185) today announced that medRxiv, a preprint platform for preliminary biomedical research, published an academic paper  on the efficacy of CanSinoBIO’s Recombinant COVID-19 Vaccine (“Ad5-nCoV”, trade name: Convidecia) as a heterologous booster against the Omicron variant. The results showed that booster vaccination with either intramuscular injection or inhaled version of Convidecia generated greater neutralizing antibody responses than those induced by the homologous inactivated vaccine booster or heterologous recombinant protein vaccine booster. A heterologous booster with one dose of Convidecia can significantly increase cellular immune protection against the transmission of and infection with the Omicron variant, and effectively prevent severe cases and immune escape.

Study Overview and Results

The study was open and parallel-controlled, with 904 participants primed with two doses of inactivated vaccines six months prior and were randomly assigned to four groups to receive one of the following boosters: one dose of Convidecia via intramuscular injection, one dose of the inhaled version of Convidecia (one fifth dosage compared to the intramuscular injection), one dose of recombinant protein subunit vaccine, and one dose of inactivated vaccine.

The study showed that boosting with either intramuscular or inhaled version of Convidecia can elicit significantly higher RBD-specific binding antibodies than those induced by recombinant protein vaccine or inactivated vaccine. 14 days following the booster vaccination, the RBD-specific antibody levels of participants were 523 (IQR, 137-1336) for the group of Convidecia by inhalation, and 464 (IQR, 210-1097) for the group of Convidecia by intramuscular injection. The results were significantly higher than the RBD-specific antibody levels of 174 (IQR, 58-488) for the group that received the recombinant protein vaccine, and 61 (IQR, 30-124) for the group of inactivated vaccine.

Strong Neutralizing Antibody Responses Against the Omicron Variant

The study observed an increased neutralizing antibody response against the wild-type SARS-CoV-2 induced by the inhaled version of Convidecia. At day 28 following the booster vaccination, the study showed an increased geometric mean titer (“GMT”) of 874 (95% CI = 569-1342) for the group of Convidecia by inhalation, 628 (95% CI = 455-868) for the group of Convidecia by intramuscular injection, while the GMTs of those in the recombinant protein vaccine and inactivated vaccine groups decreased to 210 (95% CI = 137-321) and 69 (95% CI = 51-93), respectively.

Importantly, Convidecia also demonstrated proven protection against the Omicron variant. The two groups who received Convidecia as a booster exhibited significantly higher immune responses, with a GMT of 320 (95% CI = 191-538) for the inhaled group and a GMT of 261 (95% CI = 178-382) for the intramuscular group 14 days after booster vaccination. By comparison, the GMT results of the recombinant protein vaccine and inactivated vaccine groups were 86 (95% CI = 59-127) and 54 (95% CI = 42-71), respectively.

In addition, administering Convidecia as a heterologous booster can significantly induce cellular immune responses. Notably, the inhaled version of Convidecia induced the strongest IFN-γ response among the four study groups, at 100% (95% CI, 92.6%-100.0%) and 95.7% (95% CI, 85.2%-99.5%) at day 14 and 28 following booster vaccination, respectively. The results were higher than the intramuscular Convidecia group, which were 85.4% (95% CI, 72.2%-93.9%) and 68.8% (95% CI, 53.7%-81.3%) , respectively. 

Overall, the latest study showed that administering CanSinoBIO’s Convidecia as a heterologous booster can induce stronger immune response than the recombinant protein and inactivated vaccines, stimulating greater humoral and cellular immune responses regardless of delivery route. Additionally, the inhaled version of Convidecia provides a more effective and efficient alternative for the booster vaccination program, as it can also induce mucosal immunity to achieve triple protection with only one fifth dosage of an injectable version of Convidecia.