EXPLAINED: ‘India To Have World’s First DNA Vaccine’, Here’s How The ZyCoV-D Shot Works

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Union Health Minister Mansukh Mandaviya told Parliament that India is set to become the first country in the world to roll out a DNA vaccine against the novel coronavirus . Developed by the Ahmedabad-based Zydus Cadila, ZyCoV-D  will be yet another homegrown addition to India’s vaccine arsenal.

How Soon Will The Vaccine Become Available?

Earlier this month, Zydus Cadila said it had sought emergency use authorisation from the Drug Controller General of India (DCGI) for the world’s first plasmid DNA vaccine after preliminary results from Phase-III clinical trials showed it had a 66.6 percent efficacy rate against the novel coronavirusThe New York Times said the company announced that “none of the vaccinated volunteers in the trial developed severe disease or died, making ZyCoV-D the first DNA-based vaccine shown to work against COVID-19 “.

The Phase III trials were conducted at 50 sites across the country and involved over 28,000 volunteers, the company said, adding that with the trial having been conducted during the peak of the second wave of COVID-19 in the country, it was confident about “the vaccine’s efficacy against the new mutant strains especially the delta variant”. Moreover, the vaccine was also trialled among children in the 12-18 years age group and was found to be safe.

Latest reports say that the drugs regulator has sought additional data from the company and, once it is satisfactorily reviewed, could extend the nod for the release of ZyCoV-D in August. Once launched, it will become the second indigenously made vaccine after Bharat Biotech’s Covaxin.

The company had said it plans to manufacture between 10-12 crore doses of its vaccine annually.

What Kind Of Vaccine Is ZyCoV-D?

The Zydus Cadila shot belongs to a category known as genetic or nucleic acid vaccines. These vaccines work by inserting a piece of the virus’s genetic information into the body to prompt cells to produce a key component of the virus which the immune system then recognises and attacks by producing antibodies. Genetic vaccines can be based both on RNA — like the Pfizer and Moderna mRNA shots being used in the US — or DNA.

According to US-bases think tank Milken Institute, “DNA-based vaccines work by inserting a genetically engineered blueprint of viral gene(s) into small DNA molecules (called plasmids) for injection into vaccinated people”. Once inside the human body the “cells take in the DNA plasmids and follow their instructions to build viral proteins, which the immune system recognises as foreign, triggering the immune response that protects against the disease”.

While they have become the frontline vaccine against the novel coronavirus in many countries across the world, it is the first time that any genetic vaccines have been rolled out for human use. Gavi, a public–private global health partnership working on vaccine access for poorer countries, says that “several DNA vaccines are licenced for animal use, including a horse vaccine against West Nile virus”.

What About Dosage, Storage And Delivery?

In a world of mostly two-dose COVID-19 vaccines (and the rare single dose shot like the one made by Johnson and Johnson), ZyCoV-D is, interestingly, a three-dose shot with NYT saying it is delivered four weeks apart. But the company has said that it has “also evaluated a two dose regimen for ZyCoV-D vaccine using a 3mg dose per visit and the immunogenicity results had been found to be equivalent to the current three dose regimen”.

Another novelty with ZyCoV-D is that it is an ‘intradermal vaccine’ that is applied using a “needle-free system”. That would represent a great benefit when it comes to vaccinating those who show hesitancy due to a fear of needles. Further, the absence of needles “can also lead to a significant reduction in any kind of side-effects”, the company said.

As to the logistics, the vaccine can be stored at 2-8 degrees Celsius temperatures but the company adds that it “has shown good stability at temperatures of 25 degrees Celsius for at least three months”. That would enable easy transportation and storage, unlike mRNA vaccines, which require ultra-cold storage.

How Safe Are Genetic Vaccines? How Tough Is To Produce These?

These vaccines are considered to carry no risk of causing an actual infection as they use no live components of the virus but just some genetic information encoded by it.

As to production, once the virus’s genome is sequenced, it can be quite readily produced. Gavi says that “Moderna’s RNA vaccine against COVID-19 entered clinical trials within two months of the SARS-CoV-2 genome being sequenced”. Zydus Cadila has stated that the plasmid DNA platform “provides ease of manufacturing with minimal biosafety requirements” and is also easily adaptable to target any future mutations.

Apart from Zydus Cadila, a handful of other makers across the world are exploring DNA vaccines, including Japanese biotechnology company AnGes, which has Osaka University among its partners and the US-based Inovio.



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