Mexico City— India’s drug regulator approved the world’s first DNA vaccine against Covid-19 for emergency use.
According to an interim study cited by vaccine manufacturer Cadila Healthcare, the three-dose ZyCoV-D vaccine prevented symptomatic disease in 66 percent of those immunized.
Previous DNA vaccines have worked well in animals, but not in humans.
India has so far administered more than 570 million doses of three pre-approved biologics: Covishield, Covaxin, and Sputnik V.
About 13 percent of adults have completed their cycle and 47 percent have received at least one injection since the start of the campaign in January.
Cadila Healthcare said it had conducted the largest clinical trial of the vaccine in India to date with 28,000 volunteers at more than 50 centers.
The third key phase of the clinical trials was carried out at the peak of the second deadly wave of the virus and this, according to its manufacturer, reaffirms the “efficacy of the vaccine against mutant strains”, especially the highly infectious Delta variant .
But how does this drug work and what makes it different?
DNA and RNA are building blocks of life. They are molecules that carry genetic information that is transmitted from parents to children.
Like other vaccines, it teaches the body’s immune system to fight the real virus.
ZyCoV-D uses plasmids, or small DNA rings, which contain genetic information.
These plasmids carry information to cells to produce the “spike protein,” which the virus uses to adhere to and enter human cells.
Most Covid-19 vaccines work by instructing the body to make a fragment of the spike protein to activate the immune system, causing the immune system to produce antibodies and teach itself to fight the virus.
This is the first human DNA vaccine against Covid-19.
There are a number of biologics approved in the United States, for example, for use in animals, including one for an equine disease and another for skin cancer in dogs.
Currently, more than 160 different DNA vaccines are being tested in human clinical trials in the US.
Most are for the treatment of existing cancers and a third for HIV.
ZyCov-D is also India’s first needle-free Covid-19 vaccine.
It is given with a disposable needleless injector, which uses a thin stream of the liquid to penetrate the skin and deliver the vaccine to the appropriate tissue.
Scientists say that DNA vaccines are relatively cheap, safe, and stable. They can also be stored at higher temperatures (-2 to 8 ° C).
Cadila Healthcare states that its vaccine showed “good stability” at 25 ° C for at least three months; this would help the vaccine to be easily transported and stored.
DNA vaccines developed for infectious diseases in humans have failed in the past.
“The problem is that they work well in animals. But they don’t end up offering the same level of protection in the immune response in humans, ”said Gagandeep Kang, a virologist and the first Indian woman to be elected as a member of the Royal Society of London.
The challenge, he says, was how to get plasmid DNA into the human cell to give it a lasting immune response.
Jeremy Kamil, a virologist at the Louisiana State University Health Sciences Center in Shreveport, USA, shares his vision.
“Plasmid DNA vaccines have been tried in the past. But we know that it is very difficult to get plasmid DNA into the nucleus of human cells, especially in adults, ”Kamil said.
MRNA vaccines, which use messenger RNA, a molecule to make proteins, like Pfizer or Moderna, do not need to reach the nucleus of the cell to be effective and offer greater efficacy and are likely to produce longer-lasting immunity.
The other potential drawback is that ZyCoV-D requires three doses, rather than two. The manufacturer says it is evaluating the possibility of offering two doses.
“I would love for a vaccine company to overcome the immense challenges to make it work. But it is imperative that the efficacy data is independently examined, ”Kamil concluded.