Clover Biopharmaceuticals, a Chinese biotech start-up that has developed a protein-based Covid-19 vaccine and is a supplier of Covax, said on Wednesday that trials showed the vaccine was 79 per cent effective against any severity of Covid-19 caused by the Delta variant.
The study also showed the vaccine candidate, known as SCB-2019, was 92 per cent effective against the Gamma variant and 59 per cent against the Mu variant. The overall efficacy against all the strains in the study - including the three variants, which comprised 73 per cent of the total - was 67 per cent, according to a statement released by Clover.
The vaccine was administered in two doses 21 days apart. Preliminary study shows it can be stored at temperature of 2 to 8 degrees Celsius for up to six months.
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"It is the first vaccine candidate to demonstrate significant efficacy against all three of these variants. Differences in vaccine efficacy across variant strains are driven by the unique mutation profiles of each variant, which can make some strains more transmissible and/or virulent than others and may enable immune escape," the company said.
The trials evaluated the efficacy, safety and immunogenicity of SCB-2019 in more than 30,000 adult and elderly participants in Asia, Europe, Latin America and Africa. CEPI, the Coalition for Epidemic Preparedness Innovations, funded the trials with an investment of US$328 million.
CEPI's partner Gavi, the Vaccine Alliance, a public-private partnership, announced in June an advance purchase agreement with Clover to supply up to 414 million doses for global use by next year on behalf of the Covax Facility, an initiative to provide equitable access to Covid-19 vaccines for low- and middle-income countries.
Clover, which is based in Chengdu, will provide 64 million doses of SCB-2019 this year pending emergency use approval from the World Health Organization, and Gavi has reserved the option to buy up to 350 million doses next year and vaccines that were updated for variants in the future.
"This very encouraging data demonstrates the favourable safety profile of Clover's vaccine and its efficacy against multiple variants of Sars-CoV-2, including the predominant Delta variant, so it will be a crucial addition to our weaponry in the fight against Covid-19," said Dr Richard Hatchett, CEPI's CEO.
"As a result of CEPI's partnership with Clover, this vaccine is poised to play a significant role in protecting those most at risk from Covid-19, wherever they are in the world," Hatchett said.
Earlier this month, Clover's production facility in Huzhou, Zhejiang province in eastern China, was granted a pharmaceutical manufacturing permit for production. The company said the facility would be able to produce more than 1 billion doses of antigen annually for the vaccine.
Clover plans to file for conditional approval from global regulatory authorities, including China's National Medical Products Administration, the WHO and the European Medicines Agency in the fourth quarter. If approved, it will launch the product, and if it secures emergency use listing from the WHO, it will supply 414 million doses to Covax by year's end.
The study recorded 207 symptomatic Covid-19 cases - 52 from the vaccinated group and 155 from the placebo group - at any severity occurring 14 days after the second dose of the Clover vaccine, of which 146 were genome-sequenced. All came back as variants of Sars-CoV-2, the virus that causes Covid-19.
No cases of hospitalisation caused by Covid-19 or severe illness were found in the vaccination group.
The vaccine was also found to be 100 per cent effective against severe Covid-19 and hospitalisation and 84 per cent effective against moderate to severe Covid-19 by any strain of the coronavirus in the trial.
All five cases of Covid-19 found in participants age 65 or older were in the placebo group, although the size of participants were limited because of continuing vaccination campaigns. About 18 per cent of participants randomised in the trial had co-morbidities, making them high risk for severe Covid-19, but no differences in vaccine efficacy were observed in participants with or without co-morbidities for Covid-19, the statement said.
The study found severe and serious adverse events were infrequent and balanced between the vaccine and placebo groups. Local adverse events were mostly mild and transient and decreased in frequency after the second dose. Symptoms including fatigue, headache, muscle pain, joint pain and fever were not significantly different among the two groups.
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