Single dose of Ad5-nCoV (Convidecia), a COVID-19 vaccine developed in China, is 57.5% effective against symptoms of COVID-19 and 91.7% effective against severe COVID-19 disease onset 28 days after vaccination, according to a randomized phase 3 Censored trial published in scalpel.
The report indicates that Ad5-nCoV is safe, with no serious vaccine-related adverse events or deaths reported among trial participants, and that the vaccine induces a robust antibody response.
Ad5-nCoV was developed by CanSino Biologics, Inc. and Beijing Institute of Biotechnology, a single-dose viral vector vaccine that can be stored at 2-8°C. The vaccine has been approved for emergency use in 10 countries, including Argentina, Chile, Mexico and Pakistan, where this current clinical trial was conducted. Regulatory review is underway in Russia, which also participated in this clinical trial.
“Our study shows that a single dose of Ad5-nCoV is highly effective against severe disease – and potentially help relieve the tremendous strain COVID-19 has placed on health systems around the world by preventing people from becoming seriously ill or needing to be hospitalized. Additionally, because the vaccine is effective against severe disease after a single injection, it can help improve access to vaccination, particularly in low- and middle-income countries, where it may be difficult to reach people with two doses of the initial vaccination cycle,” says the author. Principal of the study is Dr. Scott Halperin, Dalhousie University, Canada.
The trial, which is still ongoing, began on September 22, 2020, and by January 15, 2021, had enrolled 36,982 adults aged 18 and over, 36,727 of whom were randomly assigned to receive either a vaccine or a placebo injection across 66 enrollments. Locations at study centers in Argentina, Chile, Mexico, Pakistan and Russia.
The researchers performed an efficacy analysis once the protocol threshold for 150 laboratory-confirmed COVID-19 symptoms (RT-PCR) was reached 28 days after injection on January 15, 2021, at which point there were 21,250 participants in the initial efficacy cohort. The researchers reported 105 positive cases of COVID-19 among 10,590 participants in the placebo group and 45 positive cases of COVID-19 out of 10,660 participants in the vaccine group, resulting in an efficacy of 57.5% at 28 days after vaccination.
The efficacy against severe disease was 91.7% at 28 days after vaccination, where severe disease was defined as at least one clinical sign at rest indicative of severe systemic disease, respiratory failure, evidence of shock, severe renal, hepatic, or Neural. Weakness, or admission to the intensive care unit. There were no COVID-19-related deaths among the vaccine recipients.
As reported in Experiments 1 and 2 Ad5-nCoV was well tolerated and produced high levels of RBD and neutralizing antibodies.
The majority of adverse events, including injection site pain, drowsiness and headache, and general muscle pain were mild to moderate and occurred within seven days of injection. There were no reports of thrombosis or thrombocytopenia in any of the study participants.
The authors caution that the efficacy analysis was performed in samples collected on or before January 15, 2021, and therefore does not include analysis of newer variables of concern such as delta and omicron variables.
More research is needed to determine the efficacy and durability of Ad5-nCoV over a longer period of time as well as its efficacy against variants of concern, including omicron, which is rapidly exceeding delta as the dominant strain worldwide. “
Dr. Joanne Langley, Dalhousie University, Canada
The authors note that additional secondary outcomes, including efficacy against asymptomatic infections and efficacy against PCR-negative and seroconversion-positive cases, will also be analysed.
Additional research is underway to explore the relative efficacy of a single versus two dose regimen of Ad5-nCoV.
The authors note some additional study limitations. Although the study was conducted in five countries, the majority of study participants included in this analysis were from Pakistan (16,950 participants) and Mexico (13559 participants); This was mainly because the trial was first started at sites in Pakistan on September 22, 2020, followed by Mexico on November 6, 2020. People with unstable medical conditions, pregnant people, and children were excluded from the study. Women and the elderly were also underrepresented. Although the researchers used active case-finding methods through weekly contact via phone calls and text messages, the signs and symptoms were self-reported (although confirmed by in-person study visits) and thus not all positive cases were included. Further research is underway to determine Ad5-nCoV’s long-term durability and efficacy against variants of concern.
Dr. Richard Kennedy of the Mayo Clinic in the USA, who was not involved in the study, says in a related comment, “Despite the impressive achievements in SARS-CoV-2 vaccine development and production, there are still large areas of the world where vaccines still remain accessible. Limited In some regions of the world, vaccine frequency is also an obstacle to achieving high vaccination coverage. In addition to these challenges, there is weak immunity from SARS-CoV-2 vaccines and the continued emergence of variants capable of different degrees of immune evasion. Thus, there is a need It is clear and urgent for the continued development, testing and use of additional vaccines…The study provides important data supporting the continued use of another vaccine directed against adenovirus.Continuous monitoring of the study population will be essential to answer ongoing questions regarding diminished immunity, duration of protection, need for booster vaccination, and ability to Protection from new variants, including omicron.”
Halperin, SA, et al. (2021) Final efficacy, interim analysis of safety, and immunogenicity of a single dose of recombinant novel coronavirus (adenovirus type 5 vector) vaccine in adults 18 years of age and older: an international, multicenter, randomized, double-blind, controlled phase. A placebo-controlled 3-trial trial. scalpel; doi.org/10.1016/S0140-6736(21)02753-7.