Zydus' Covid-19 vaccine shows 66.6% efficacy, seeks DCGI approval

Phase 3 trial for the vaccine had more than 28,000 volunteers-the largest such exercise in India, says company.

In what could be the world’s first approved deoxyribonucleic acid (DNA)-plasmid vaccine, Ahmedabad-based Cadila Healthcare’s three-dose vaccine ZyCoV-D is expecting a nod from India’s drug regulator. The vaccine has shown 66.6 per cent efficacy in interim analysis of Phase 3 trials, and can be stored at 25 degrees Celsius for three months.

No moderate case of Covid was observed in the vaccine arm after administration of the third dose, suggesting 100 per cent efficacy for moderate disease. No severe cases or deaths due to Covid occurred in the vaccine arm after administration of the second dose of the vaccine, the company claimed.

ZyCoV-D efficacy is in the range of Johnson & Johnson’s single-dose vaccine, which uses a human adenovirus vector Ad26 — a 66.3 per cent efficacy in preventing Covid.

As for the Oxford-AstraZeneca vaccine, the World Health Organization notes on its website, “The AZD1222 vaccine against Covid has an efficacy of 63.09 per cent against symptomatic SARS-CoV-2 infection.”

Covaxin has shown 77.6 per cent efficacy against symptomatic Covid illness from interim analysis of Phase-3 trials, while Sputnik V has shown 97.8 per cent efficacy against severe Covid disease in a trial on 81,000 subjects in the UAE.  

Zydus has submitted safety and tolerability data on adolescents from Phase 2 clinical trials, and has generated the data on 1,000 adolescents (between 12 and 18 years) from its Phase 3 trials too.

“We intend to submit this immunogenicity data (whether the vaccine induces the desired immune response) in four weeks to the drug regulator,” said Sharvil Patel, MD of Zydus Cadila.

If things go well, ZyCoV-D could be the first approved vaccine for adolescents. Zydus has also claimed that its vaccine works against the Delta variant. 

The trials carried out in more than 50 clinical sites and during the peak of the second wave have shown the vaccine’s efficacy against the new mutant strains, especially the Delta variant.

Zydus has submitted the immunogenicity data from a two-dose regimen (using 3 mg doses) trial to the Drugs Controller General of India, which shows ‘equivalent immunogenicity’ with that of the three-dose regimen.

Patel is hopeful of a ‘good discussion point’ with the regulator for approval of a two-dose regimen. The efficacy trial on 28,000 volunteers was on the three-dose regimen given on Day Zero, Day 28, and Day 56. Zydus has invested Rs 400-500 crore in developing the ZyCoV-D so far, which includes setting up of manufacturing plants.

“We have repurposed an existing plant where we are now producing, and our new plant will be ready by the end of July. By August, we should have the capacity to make 10 million doses a month and by the end of this year, we would have made 50 million doses of ZyCoV-D,” said Patel.

 Conventional active vaccines are made of a weakened form of the infectious agent. DNA plasmid vaccine is a relatively new approach where a strand of DNA containing the genes for the antigens is injected. 

The body then learns to develop an immune response against the antigen, and when the actual pathogen attacks, the body is able to generate the specific antibodies against it. 

DNA vaccines, Zydus has claimed, have been shown to stimulate sustained immune responses.

It has not stockpiled vaccines, and expects the vaccine may be available in 45-60 days in the market once the nod comes in. The pricing, the company says, will be made public closer to the commercial launch.