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EXPLAINED | The Science Behind Covid-19 Vaccines Approved by India

File photo of Bharat Biotech's Covaxin.

File photo of Bharat Biotech's Covaxin.

Official data has shown that only 11% of India's population has received at least one vaccine dose while just 3.4% have completed the required two doses.

Indian drugmaker Zydus Cadila said on Thursday it has applied to the country’s drug regulator for emergency use approval of its Covid-19 vaccine, which showed a 66.6% efficacy against positive cases in an interim analysis. The candidate, if approved, would become India’s second successful home-grown Covid-19 shot and help ease the country’s severe vaccine shortage. The development comes a day after Cipla on Tuesday received the approval from the Drugs Controller General of India (DCGI) to import Moderna’s coronavirus vaccine for restricted emergency use in India.

Even as experts say that the children rarely develop severe forms of Covid-19, the states of Karnataka and Maharashtra have recently witnessed a spike in paediatric Covid cases, and some deaths too. Not only instances of coronavirus, but cases of paediatric black fungus were also reported in the past two months.

After the second wave wreaked havoc across India, Experts believe that vaccines are the best way forward for India, which launched its mass inoculation program in January. Since then, official data showed that only 11% of the population has received at least one vaccine dose while just 3.4% have completed the required two doses. While India’s urban population that bore the brunt of overwhelmed health infrastructure during the second wave has been actively getting jabs but the authorities face a serious challenge in inoculating its rural population.

However, some studies, including lab-based work and analysis of real-world data, have suggested current Covid vaccines are somewhat less effective against the Delta variant than the Alpha variant. The experts also claim that the “vaccines protect, and a second dose is very important against the Delta variant”, reported The Guardian.

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Also Read: Zydus Cadila May Soon Seek Emergency Use Authorisation for Covid-19 Vaccine

Here’s how the science behind these vaccines work

Zydus: An approval for the vaccine, ZyCoV-D, would make it the fifth shot authorised for use in India in what is touted to be the world’s first Plasmid DNA vaccine. With ZyCoV-D, the Indian firm has established a DNA vaccine platform that uses a non-replicating plasmid, which carries the gene of interest. It means that the vaccine will push the body to build antibodies against the coronavirus, as the inserted DNA sequence will match the sequence pattern of the virus. According to a report by The Print, the plasmid DNA is introduced into the host cells, where it is translated into the viral protein and elicits a strong immune response mediated by the cellular and humoral arms of the human immune system.

Covaxin: Bharat Biotech partnered with the National Institute of Virology (NIV) and the Indian Council of Medical Research (ICMR) for the ‘inactivated coronavirus’ vaccine Covaxin. Trial results have shown the vaccine has an efficacy of 78 per cent. Pathogens (viruses or bacteria) that cannot multiply can be injected into the arm without causing covid-19 inside the body. Using chemicals like formalin, the vaccine works by teaching the immune system to make antibodies against the SARS-CoV-2 coronavirus.

The inactivated viruses are then mixed with a tiny amount of an aluminum-based compound called an adjuvant which stimulates the immune system to boost its response to a vaccine. At Least 55 crore doses of Covaxin would be available by December, the government said.

Covishield: The University of Oxford partnered with the British-Swedish company AstraZeneca developed a vaccine based on the ‘viral-vectored platform.’ The Serum Institute of India is manufacturing the vaccine known as Covishield in India. Viral vector-based vaccines don’t actually contain antigens but rather use the body’s own cells to produce them. It uses a modified virus (the vector) to deliver genetic code for antigen in the case of COVID-19 spike proteins found on the surface of the virus, into human cells.

The coronavirus spike protein gene is added to two types of adenovirus, one called Ad26 and one called Ad5, to enable them to invade cells but not replicate. Once infected, the cells make large amounts of antigen, triggering an immune response against the virus. The Oxford-AstraZeneca vaccine uses a chimpanzee adenovirus because humans will not have pre-existing antibodies to this adenovirus. Over 75 crore doses will be made available by the SII between August and December.

Sputnik V: Russian Ministry of Health’s Gamaleya Research Institute developed a ‘non-replicating viral vector’ coronavirus vaccine Sputnik V. The two-dose vaccine has an efficacy rate of 91.6 per cent. Sputnik V uses two human adenoviruses Ad5 and Ad26, the adenoviruses bump into cells and latch onto proteins on their surface. Once injected into the body, these vaccine viruses begin infecting our cells and inserting their genetic material – including the antigen gene – into the cells’ nuclei. Human cells manufacture the antigen as if it were one of their own proteins. At least 15.6 crore doses will be available in India by December.

Moderna: Cipla, a multinational pharmaceutical company headquartered in Mumbai, on Tuesday received the approval from the Drugs Controller General of India (DCGI) to import Moderna’s coronavirus vaccine for restricted emergency use in India. Moderna’s method to protect against Covid-19 relies on messenger RNA (mRNA) to program cells to generate immunity to the coronavirus. This vaccine along with Pfizer are viewed as a preferred choice among wealthy countries, analysts said, based on clinical trial data showing they were more than 90% effective at preventing symptomatic coronavirus.

Also Read: India Reports Lowest Covid Cases Since April 1; Maharashtra, Bengal See Uptick | 10 Points

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