BEIJING (Reuters) – CanSino Biologics Inc’s vaccine was 57.5% effective against symptomatic COVID-19 and 91.7% against severe disease four weeks or longer after one dose, while its protection appeared lower in older people, peer-reviewed results from a large trial showed.
The single-shot Ad5-nCoV vaccine, which CanSinoBIO co-developed with the Chinese military-backed Beijing Institute of Biotechnology, has been approved for use in countries such as China, Mexico and Pakistan.
The efficacy of 57.5% against symptomatic COVID-19, meaning it reduced the risk of symptomatic disease by 57.5% for vaccinated people as compared with the unvaccinated, came from analysis of 150 cases in a cohort of over 20,000 healthy adults in a Phase III clinical trial, wrote researchers.
The study, published on Thursday in the Lancet medical journal, did not look at how recent variants such as Delta and Omicron would affect the vaccine’s effectiveness.
The shot’s efficacy against any symptomatic infection beginning 28 days after injection was much lower in those aged 60 and older, at 17.5%. Efficacy against severe disease was 76.1% for the age group.
The authors cautioned that the older group’s small sample size made the analysis for that subgroup more likely to be imprecise compared with the overall efficacy.
Richard Kennedy, a vaccine researcher at the Mayo Clinic who wrote an editorial accompanying the study, said the 17.5% figure indicates that additional doses might be necessary for the elderly.
CanSinoBIO is studying an inhalation version of Ad5-nCoV, and a two-dose regimen.
The overall efficacy beginning 14 days after one dose was higher than at 28 days, at 63.7% against symptomatic COVID-19 and 96.0% against severe disease.
There were no vaccine-related serious adverse events or deaths from the trial or reports of vaccine-induced thrombotic thrombocytopenia (VITT), extremely rare cases of clotting with low platelets that have been associated with other adenovirus-vector vaccines.
Ad5-nCoV is based on a similar technology to that of Russia’s Sputnik V and vaccines from Johnson & Johnson and AstraZeneca.
(Reporting by Roxanne Liu and Ryan Woo; editing by Christine Soares, Caroline Humer and Chizu Nomiyama)