Zydus’ COVID-19 Vaccine Efficacy Shows Promise for DNA-Based Vaccines

India’s Zydus Cadila is appealing to regulators to grant emergency use authorization for the drugmaker’s three-dose DNA-based COVID-19 vaccine after interim study findings showed the vaccine was 66.6% effective at preventing COVID-19. 

The vaccine, dubbed ZyCoV-D, will be the first DNA vaccine available in the world if authorized by regulators. Zydus’s ZyCoV-D uses a portion of DNA found in the novel coronavirus to elicit an immune response against the spike protein found on SARS-CoV-2. 

In a statement made by Zydus, the most recent interim findings from a late-stage trial showed the vaccine was 66.6% effective at preventing symptomatic disease in 28,000 volunteers. The study cohort also included 1,000 volunteers between the ages of 12 and 18. The company plans to submit immunogenicity data for the adolescent participants in the next four to six weeks.

The company added that additional immunogenicity results show a two-dose regimen of the vaccine is equal to the three-dose regimen but didn’t divulge further details on these findings.

“This breakthrough marks a key milestone in scientific innovation and advancement in technology,” said Cadila Healthcare’s managing director, Dr. Sharvil Patel, in a statement. “This has been possible because of the collective support of the government, the regulators, the volunteers who had faith in the process, the investigators who conducted the multi-centric trials all through these months, the suppliers who worked closely with us and our dedicated team of researchers and vaccine professionals who worked tirelessly on the vaccine and also manufactured the trial doses.”

Approval of the three-dose shot will also make it the fifth vaccine to be authorized for use in India, a country that has been recently hard hit by the ongoing pandemic. As reported by Reuters, Zydus hopes to have the capacity to produce 10 million doses of the vaccine by mid-August.

DNA-based vaccines like ZyCoV-D are receiving interest by vaccine makers in hopes they can harness similar discoveries made in the development of the novel mRNA vaccines. To date, DNA vaccines have only been approved for use in veterinary medicine, as human immune responses to these vaccines have not been sufficient enough to provide adequate protection. 

This hasn’t stopped companies and researchers from trying to develop DNA vaccines, however, especially for COVID-19. As reported in a May edition of PLOS Neglected Tropical Diseases, researchers found one DNA vaccine effectively protected mice and hamsters from developing COVID-19 after they were exposed to SARS-CoV-2.

A Phase I clinical study launched in Australia is studying a needle-free DNA COVID-19 vaccine called COVIGEN. The needle-free component was designed by PharmaJet, given the company’s needle-free injection systems reportedly increase the efficacy of DNA vaccines.

In April, Inovio announced its DNA vaccine INO-4800 produced robust responses against several COVID-19 variants, including the U.K. and Brazil variants, in a study. Positive interim data reported last year showed 94% of vaccine recipients in a Phase I trial demonstrated an overall immune response by week 6 following two doses. The vaccine was also reportedly safe and well-tolerated by week 8, with no serious adverse events reported. 

DNA-based vaccines, if proved effective in humans, could offer advantages over mRNA vaccines in that DNA COVID-19 vaccines are stable at room temperature, improving the ease at which the shots can be transported and stored.