Recently, India approved a new COVID-19 vaccine, ZyCoV-D, which uses a circular DNA strand to stimulate the immune system against the SARS-CoV-2. The approval of ZyCoV-D as the world's first DNA vaccine for humans heralds the arrival of DNA vaccines against various diseases.

According to Nature, ZyCoV-D can enter the skin without the use of a needle, which has a 67% protection rate in clinical studies for symptomatic patients with COVID-19, and could be utilized in India this month.

The researchers said that although its effectiveness is not particularly high compared with many other COVID-19 vaccines, it is of great significance as a DNA vaccine ( itself.

Peter Richmond, a pediatric immunologist at the University of Western Australia, said this proves that the DNA vaccine is effective and helps control the COVID-19 pandemic. "This is a crucial step forward in the global fight against the new coronavirus, because it shows that we have another type of vaccine to use." He said.

Nearly a dozen DNA COVID-19 vaccines are currently in clinical trials around the world, with at least as many are in early stages of development. DNA vaccines are also being developed for a variety of different diseases. "If DNA vaccines prove viable, this will be the future of vaccinology because they are easy to make," says Shahid Jameel, a virologist at Ashoka University in India.

According to David Weiner, director of the Center for Vaccines and Immunotherapy at the Wistar Institute in Philadelphia, Pennsylvania, "the urgency of combating COVID-19 has hastened the development of vaccines using genetic technologies, such as messenger RNA vaccine (mRNA vaccine) and DNA vaccine."

In clinical trials, RNA vaccines were found to be more effective at eliciting a significant immune response. However, DNA vaccines have several advantages, including the ease with which they may be made and the fact that the finished product is more stable than mRNA vaccine that must typically be stored at extremely low temperatures.

ZyCoV-D was developed by Zydus Cadila, an Indian pharmaceutical company based in Ahmedabad. Recently, the Indian drug regulator approved the vaccine for use in people aged 12 years and older. 67% of the effectiveness data came from a clinical trial that included more than 28,000 participants. In the trial, 21 symptomatic cases of COVID-19 were seen in the vaccination group and in 60 patients receiving placebo.

ZyCoV-D comprises plasmids, which are circular DNA strands capable of altering the SARS-CoV-2 spike protein as well as the promoter sequence of the initiation gene.

When plasmids reach the nucleus, they are transcribed to mRNA which then travels to the cytoplasm, the cell's main body, and is translated into the stinger protein. The body's immune system then responds to this protein and produces “tailor-made” immune cells that blockade future infections. The plasmids usually degrade within weeks to months, but the immunity remains.

The challenge with DNA vaccine is that it needs to reach the nucleus, whereas mRNA vaccine only needs to reach the cytoplasm to take effect, Jameel said. For a long time, DNA vaccines have had difficulty inducing an effective immune response in clinical trials, which is why so far they have only been licensed for use in animals, such as horses.

ZyCoV-D effectively addresses this issue by settling beneath the skin rather than deep inside muscle tissue. Immune cells abound in the subcutaneous area, engulfing and processing foreign things such as vaccination particles.

This vaccination is administered by pressing a needleless device against the skin, which generates a thin stream of high-pressure fluid that pierces the skin surface and causes less pain.

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