Covid-19: Zydus gets SEC approval for two-dose regimen of ZyCov-D

Zydus to conduct mixing trials to test vax efficacy after two shots of Covishield/Covaxin

Zydus Lifesciences’ (formerly known as Cadila Healthcare) three-dose Covid vaccine — ZyCoV-D — has received the subject expert committee (SEC) approval for a two-dose regimen, according to sources close to the development.

The pharmaceutical company, however, declined to comment on the matter.

Approval for the two-dose regimen may boost the offtake of the vaccine not yet available in the private market.

Zydus Lifesciences supplies its three-dose deoxyribonucleic acid (DNA) vaccine — ZyCoV-D — to the Centre at Rs 265 per dose and the needle-free applicator device at Rs 93 per dose. It had an order for 10 million doses from the Centre. The vaccine is not available in the private market.

Meanwhile, sources also indicated that Zydus was planning to do clinical trials to check its vaccine performance as a third precautionary shot after a two-dose regimen of either the Covaxin or Covishield. “This will require studies to check the results of mixing the vaccines. ZyCoV-D will be tested as the third dose,” said a source in the know.

Zydus had indicated last year that it was seeking the drug regulator’s nod for a two-dose regimen for ZyCoV-D which has shown 66.6 per cent efficacy in the interim analysis of Phase 3 clinical trials, and can be stored at 25 degrees Celsius for three months. 

The company had claimed that 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, it had said.

Last July, Zydus had submitted the immunogenicity data from a two-dose regimen (using 3 milligram doses) trial to the Drugs Controller General of India (DCGI). Sharvil Patel, MD, Zydus Cadila, had said the data showed ‘equivalent immunogenicity’ with that of the three-dose regimen.

Eventually, more data has been submitted to the DCGI, and the two-dose regimen data has been reviewed from time to time.  Conventional active vaccines are made from 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. 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.  Zydus has invested Rs 400-500 crore in developing the ZyCoV-D so far, which includes setting up of manufacturing plants.