Decoded: How Does India’s 2nd Homegrown Zydus Cadila Vaccine Work

In phase 3 of trials, Zydus’ ZyCoV-D could become India’s 2nd fully homegrown vaccine in use. Here’s what we know.

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As India gears up to roll out another potential COVID vaccine, here’s everything you should know about it.
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As COVID-19 surges, so has the race for vaccination accelerated. While in the last few months, a number of vaccines have been developed the world over, India has only authorised two vaccines, Bharat Biotech’s Covaxin, and Oxford AstraZeneca’s Covishield, for public use.

But this might change sooner than we anticipated.

ZyCoV-D, developed by Ahmedabad-based Indian Pharmaceutical company Zydus Cadila could become India’s second fully homegrown vaccine to be rolled out for public use, as early as next month.

The Zydus Cadila vaccine, which is unique from its predecessors, is in phase III of clinical trials, the results of which could make a significant impact on India’s ongoing inoculation drive.

But how much do you know about the indigenous vaccine?

What kind of a vaccine is it? How does it compare to Covaxin and Covishield? When will we get it? FIT gets you up to speed on everything we know about the vaccine.

What type of vaccine is ZyCoV-D?

ZyCoV-D is a Plasmid DNA vaccine.

The DNA (And RNA) vaccines—a relatively new technology developed for the first time only in the 1990s—don't introduce a weakened form of the pathogen like traditional vaccines.

Instead, this type of vaccine works by carrying the genetic code of the virus. The plasmid vector is taken up into cells and transcribed in the nucleus. This is transferred to another mRNA molecule, which induces a cell-mediated immune response.

The Zydus vaccine is the first DNA vaccine to be produced in India.

In theory, DNA vaccines produce the same results as mRNA vaccines, and so the efficacy of the Zydus vaccine too is likely to be in the realm of the other mRNA vaccines already in the market, including Moderna, Pfizer, and Johnson & Johnson.

One advantage that DNA vaccines have over their mRNA counterparts is that they are more stable in higher temperatures, making them more suitable for use in warmer countries like India.

“Furthermore, the (DNA vaccine) platform can be rapidly used to modify the vaccine in couple of weeks in case the virus mutates to ensure that the vaccine still elicits protection

DNA vaccines work by introducing the genetic coding of the virus to the immune system to induce an immune response.
DNA vaccines work by introducing the genetic coding of the virus to the immune system to induce an immune response.
(Photo: NCBI)

At what stage is the vaccine?

In July of 2020, Cadila Healthcare Limited announced that their vaccine for COVID-19, named ZyCoV-D, successfully completed preclinical development and had received permission to initiate human clinical trials.

On 24 December, the company submitted the results of Phase I/II clinical trials conducted in over 1000 healthy adult volunteers.

On 3 January, they announced that their vaccine had received approval from the Drugs Controller General of India (DCGI) to start Phase III Clinical Trial of ZyCoV-D –

“The launch of the Phase 3trial will determine the efficacy of our vaccine in preventing COVID-19 which continues to pose a major threat, the world over.”   
Pankaj R. Patel, Chairman of the Zydus Group  

In their latest statement, the company informed that the dosing for the Phase III clinical trials has started in 60 locations, on 30,000 healthy adult volunteers.

The results of the trial, and the actual efficacy of the vaccine, are yet to be announced.

How is it different from Covaxin and Covishield?

  • Zydus vaccine has the same goal, and is likely to have the same results as the two existing homegrown vaccines, but where it differs is in the way it works.

Covaxin is a whole inactive virus type vaccine, and Covishield is a non-replicating viral vector type vaccine.

Both of which are relatively traditional, well established types of vaccine technology that work by introducing a part (in the Oxford vaccine it is the gene protein spikes found on the virus’ surface) or whole of the virus in a ‘harmless’ form to trigger the immune system into producing a large number of antigens to fight the actual virus.

The Zydus vaccine, as explained, is a DNA vaccine that delivers only a specific set of instructions to our cells that instructs our immune system to recognize and respond to the virus.

The Zydus vaccine is also India’s first plasmid DNA vaccine.

  • Unlike Covishield and Covaxin, ZyCoV-D is being tested as a 3 dose vaccine.
  • While it can be stored in normal refrigerator temperatures of 2 - 8 degrees Celcius like Covishield and Covaxin, the company also claims that the vaccine is very thermostable at up to 25 degrees.

How safe is it?

While Phases I and II of the trials showed no side effects, it's still too early to say how it compares to the other two vaccines that have cleared all three phases of clinical trials.

In the results submitted by the company, ZyCoV-D was found to be safe, well-tolerated, and immunogenic in the Adaptive Phase I/II clinical trials.

“The Phase II study of the vaccine ZyCoV-D had been conducted in over 1000 healthy adult volunteers. The vaccine was found to be safe and elicit a strong immunogenic response”, it reads.

When will it be available?

‘The Zydus vaccine will be available for use in 4-6 weeks’, Dr NK Arora, Head of the Operations Research Group of the COVID-19 Task Force told CNBC-News 18.

Zydus Cadila hopes to produce 100-150 million doses by end of 2021.

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