New Delhi: The phase 3 clinical trial of the world’s first DNA-based vaccine ZyCoV-D have shown that the needle-free, three-dose vaccine has an efficacy of 66.6 per cent, according to the results published Friday in The Lancet journal.
Although Indian regulatory authorities have approved Zydus Lifesciences’ (formerly known as Cadila Healthcare) ZyCoV-D for children over 12, the vaccine is yet to be rolled out in the country.
Developed in 2020, preliminary animal study demonstrated that the vaccine induces antibody response including neutralising antibodies against SARS-CoV-2. Subsequent phase 1 and phase 2 trials in 1,048 human volunteers found the vaccine to be safe.
The vaccines contain a genetically engineered plasmid — a small DNA molecule that can replicate independently. The plasmid is engineered to produce the spike protein of the virus, which then triggers a protective immunological response.
DNA-based vaccines do not need a SARS-CoV-2 virus strain, unlike the inactivated vaccines that require viruses in killed or inactivated forms. This makes developing the virus much simpler as it can be manufactured under minimal biosafety requirements.
In the absence of any infectious agent in the vaccine, it can be manufactured with ease, under minimal biosafety requirements (BSL-1).
ZyCoV-D is delivered using a needle-free injection device.
The trial of the vaccine, conducted in India, is the first phase 3 trial globally to deliver a DNA vaccine using a needle-free delivery device, and the first time that a COVID-19 vaccine is being tested in the age group of 12–17 years in India.
Overall, the study demonstrated that intradermal injection of ZyCoV-D vaccine is safe and feasible and might achieve successful prevention of COVID-19 diseases in a large population.
“Additionally, the DNA vaccine is based on a plasmid DNA platform, which allows rapid generation of new constructs; the ZyCoV-D vaccine can therefore pave the way for next-generation DNA vaccines capable of handling mutant strains,” the authors wrote in their study.
“We anticipate that the major implication of this study will be the introduction of DNA-based prophylactic therapy against highly infectious diseases such as SARS-CoV-2,” they said.
The study showed that a three-dose regimen of ZyCoV-D, administered intradermally via a needle-free injection system, was found to be 66.6 percent effective against Covid-19.
The study was conducted during the peak of the second wave of COVID-19 in India, which was mainly due to the B.1.617.2 (delta) variant. As many as 27,703 volunteers participated in the trial, of which 13,851 were given the vaccine, while the rest were given a placebo.
The team, which included doctors from Grant Government Medical College, Sir J J Group of Hospital in Mumbai, N R R Hospital in Bangalore, and Cadila Healthcare, conclude that the ZyCoV-D vaccine is effective against the delta variant.
“Considering that no severe or moderate COVID-19 cases were reported in the ZyCoV-D group, and based on the interim analysis results, the vaccine was found to be 100% effective against severe and moderate COVID-19 cases and 64·9% effective against mild COVID-19 cases,” the researchers said.
“Therefore, it is possible that the severe and moderate cases that might result in fatalities and put enormous pressure on health-care systems could be prevented to a great extent with full vaccination using the ZyCoV-D vaccine,” according to the study.
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