All you need to know about ZyCoV-D, The indigenous plasmid DNA COVID vaccine, Approved in India

The Subject Experts Committee (SEC) of the Central Drugs Standard Control Organisation (CDSCO) has recommended Cadila Healthcare’s (Zydus Cadila) ZyCoV-D vaccine, clearing a major hurdle for the vaccine’s emergency use.

If approved by the Drug Controller General of India (DCGI), ZyCoV-D will become the world’s first plasmid DNA COVID-19 vaccine to be approved and the second indigenous vaccine to be rolled out.

Here is an explainer on its safety, efficacy, delivery, and capacities.

Safety and efficacy

Zydus said ZyCoV-D exhibited robust immunogenicity, tolerability, and safety profile in the adaptive Phase I/II clinical trials. The three doses (2mg per dose) of the vaccine were found to have an efficacy of 66.6 percent for symptomatic RT-PCR positive cases in the interim analysis.

Zydus said it had found no severe cases on the COVID arm or deaths due to COVID-19 after administering the second dose of the vaccine. No moderate case of COVID-19 was observed in the vaccine arm post the administration of the third dose, suggesting 100 percent efficacy in moderate cases.

A ‘Covid arm’ refers to a rash that may appear after receiving the vaccine. The Phase-3 clinical trials were conducted on over 28,000 volunteers in more than 50 clinical sites spread across the country and during the peak of the second wave of COVID-19, reaffirming the vaccine’s efficacy against the new mutant strains, especially the Delta variant. The company said the study also shows that ZyCoV-D is safe for children aged 12-18 years.

Needle-less vaccine
The vaccine is delivered through a needle-free applicator called the PharmaJet to ensure painless intradermal vaccine delivery. Moneycontrol learns that this device was developed in India in a record time.

Capacity

Zydus said it could produce 10-15 million doses of ZyCoV-D per month. The company said it could produce 3-5 crore vaccines by December. The capacity numbers suggest that Covishield and, to some extent, Covaxin will remain as the major workhorses for the government’s vaccination drive for some more time.

Evaluating two-dose regimen

Zydus said it has also submitted data for a two-dose regimen for ZyCoV-D, using a 3 mg dose per visit. The immunogenicity results were equivalent to the current three-dose regimen. The company said this would help reduce the full-course duration of vaccination while maintaining a high safety profile in the future.

Children & adolescents

Zydus has submitted applications for EUA for children in the 12-18 year age group.

Novel approach

Zydus Cadila has taken a novel approach for its potential COVID-19 vaccine. Called plasmid DNA, the vaccine consists of the genetic material of SARS-CoV-2 proteins, which instruct human cells to make the SARS-CoV2 antigen, eliciting an immune response.

The company says that this approach is easily replicable and scalable, requiring just Biosafety Level (BSL)-1. The vaccine can be stored at 2-8 degrees, making it conducive to Indian cold-chain conditions. The vaccine is delivered through the intradermal route (between the layers of the skin), which makes its administration much easier. DNA vaccines are also theoretically easy to redesign quickly against a mutating virus.

Challenges

Firstly, the platform is novel. Not a single human vaccine using this platform has been approved anywhere in the world. The other big challenge is that the vaccine must be administered in three doses – the first and the other doses after 28 and 56 days.

Being a three-dose vaccine adds a layer of distribution and administration complexity, possibly raising the cost of the vaccine. While the company has promised to ensure that the vaccine is affordable, it has also sought approval for a two-dose vaccine.

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