The Convidecia COVID-19 vaccine has demonstrated high immunogenicity and safety in the local Phase III clinical trial in Russia. Data was presented in the final study report sent by Petrovax to Russia’s Ministry of Health in early August. According to the study, one dose of the vaccine provides a pronounced immune response, with favorable tolerability and a high safety profile.
The volunteers from the vaccine group had high titers of antibodies against full-length SARS-CoV-2 Spike protein, with a geometric mean titre (GMT) of 676,86 and with 90.6% of participants seroconverted by the 28th day. During the entire observation period, the level of neutralizing antibodies remained high with GMT levels of 19,50 in 48,9% of participants which showing evidence of long-term protection.
The local clinical trial was approved by Russia’s Ministry of Health on August 14 2020, started in September, and was completed on May 5, 2021 with all the protocol examinations and validation conducted during the six-month observation period. The researchers analyzed the data from the 496 volunteers aged from 18 to 85 years, including 372 participants from the Convidecia vaccine group and 124 volunteers from the placebo group.
The study evaluated the effect of preexisting immunity to the adenoviral vector on vaccine immunogenicity in a small subset of the participants. The amount of antibodies to the Ad5 vector at the time of vaccination did not affect the level of seroconversion, which was the main indicator of immunity to SARS-CoV-2. This data suggests that the immune response to SARS-CoV-2 does not depend on the person's pre-existing immunity to adenovirus.
During the trial, post-vaccination systemic reactions were reported by 26.9% and 10.5% of volunteers in the study group and placebo group respectively. Most frequently observed symptoms in the vaccine recipients were fever in 20.2%, headache in 5.9%, fatigue in 5.4%, and muscle pain in 4.8%, and joint pain in 1.9%.
Most volunteers in both groups had mild general and local post-vaccination reactions and adverse effects that did not last more than 7 days after the vaccination. Local post-vaccination reactions were detected in 21.8% of the study participants. 21% of the volunteers in the study group experienced mild systemic reactions and 4.6% experienced moderate reactions.
There were no serious adverse reactions in the vaccinated group and no fatalities reported in the trial. There was no withdrawal from the study due to any adverse events.
The Convidecia COVID-19 vaccine is a recombinant vaccine based on the adenovirus type 5 vector expressing SARS-CoV-2 Spike protein and developed by CanSino Biologics Inc. (СanSinoBIO, SHSE: 688185, HKEX: 06185), China’s leading biopharmaceutical company.
Convidecia is a one-shot vaccine stored at 2-8 °C. The vaccine has received an emergency use authorization (EUA) by the regulators and used for mass vaccination in, Hungary, Argentina, Mexico, Pakistan, Malaysia, Chile, and conditional marketing authorization in China.
The previous interim analysis of data on the first 200 patients included in the local Phase III clinical trial in Russia and examined 28 days after the vaccination showed a high immune response after one-shot Convidecia immunization — high COVID-19 antibody titers (GMT of 672,67) were detected in 92.5% of the volunteers.
In addition to a local study in Russia, an international, placebo-controlled Phase III trial is being conducted to evaluate the efficacy and immunogenicity of Convidecia, with 5,418 volunteers in Russia (Over 40,000 volunteers globally). This study is aimed to assess the vaccine efficacy during the long-term 12 months observation.