A coronavirus vaccine made from pure DNA has been approved in India for the first time in the world.
The vaccine is supposed to be effective and has few side effects. But the drug raises concerns.
Benefits of DNA vaccines
Like Biotech and Moderna mRNA vaccines, the ZyCoV-D vaccine from Indian pharmaceutical company ZydusCadila contains a piece of genetic material with information about the structure of the spike protein of the coronavirus, which should trigger the human body’s immune response. But the information about the protein’s structure is not present in the form of mRNA, but as pure DNA. In ZyCoV-D, however, the viral DNA fragment is not located on the chromosome but forms a small ring (“plasmid”).
From the experts’ point of view, the registration of the Indian vaccine is a real technological breakthrough. “The fact that this technique now also works in humans is a great success,” says Leif Eric Sander, who heads the Infectious Immunology and Vaccine Research Working Group at the Charite Clinic in Berlin. Until now, the principle has only been used in veterinary medicine.
“DNA vaccines have many advantages,” Sander says. Because DNA can be produced cheaply and on a large scale, and it’s also very stable. These vaccines, unlike mRNA vaccines, don’t need special storage conditions. Therefore, even before the pandemic, the World Health Organization recommended betting on the use of DNA vaccines in poorer and warmer countries. At least 160 drugs are currently in development.
However, DNA technology also has disadvantages. DNA is a precursor of mRNA in the body. Therefore, in order for these vaccines to work, an extra step is required: whenever the body uses information from DNA, it must first transcribe it into mRNA; only then can it build proteins with mRNA — such as the coronavirus spike protein in the case of the ZyCoV-D vaccine, which then triggers an immune response and thus creates immune protection against the real infection.
“Probably because of this extra step, DNA vaccines are less effective than mRNA vaccines,” says Karsten Watzl, general secretary of the German Society for Immunology. After all, to translate into mRNA, vaccine DNA must penetrate deep into human cells — right up to the cell nucleus. But its envelope is difficult to overcome. “This is an obstacle that complicates this technology,” Watzl says.
Thus, India’s coronavirus vaccine is nowhere near as effective as mRNA vaccines, which provide more than 95 percent protection against symptomatic coronavirus infection. In a registration trial involving 28,000 subjects, the ZyCoV-D vaccine achieved only 66 percent efficacy.
“However, the study was conducted when the delta variant of the coronavirus was already spreading in India,” Sander emphasizes. According to the manufacturer, ZyCoV-D also has extremely mild side effects, but the relevant scientific data have not yet been published.
To increase the vaccine’s effectiveness, it is not injected into the muscle with a needle. It is injected under the skin with a kind of inoculation “gun.
However, the fact that the vaccine DNA reaches the cell nucleus and is thus very close to human DNA raises concerns. At the very least, we can assume that the vaccine DNA is embedded in the human genome.