Vaccination in India
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In India, for the first time in the world, a coronavirus vaccine made from pure DNA has been approved.
The vaccine is believed to be effective with few side effects. But the drug raises concerns.
Advantages of DNA vaccines
Like the mRNA vaccines from Biontech and Moderna, the ZyCoV-D vaccine from the Indian pharmaceutical company ZydusCadila contains a piece of genetic material with information about the structure of the coronavirus spike protein, which should prompt the human body to an immune response. But information about the structure of a protein is present in it not in the form of mRNA, but in the form of 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. “It is a great success that this technique is now working in humans,” says Leif Erik Sander, who leads the Infectious Immunology and Vaccine Research Working Group at Charité Berlin. Until now, this principle has only been applied in veterinary medicine.
“There are many benefits to DNA vaccines,” says Sander. Because DNA can be produced cheaply and on a large scale, and it is also very stable. Such vaccines, unlike mRNA vaccines, do not require special storage conditions. Therefore, even before the start of the pandemic, the World Health Organization recommended betting on the use of DNA vaccines in poorer and warmer countries. Currently, at least 160 drugs are in development.
disadvantages
However, DNA technology also has disadvantages. DNA is the precursor to mRNA in the body. Therefore, for these vaccines to work, an additional step is required: whenever the body uses information from DNA, it must first transcribe it into mRNA; only then can he build proteins using mRNA – for example, the spike protein of the coronavirus in the case of the ZyCoV-D vaccine, which then triggers an immune response and thus creates an immune defense against a real infection.
“It is probably because of this extra step that DNA vaccines are less effective than mRNA vaccines,” says Carsten Watzl, general secretary of the German Society for Immunology. Indeed, for translation into mRNA, vaccine DNA must penetrate deep into human cells – right down to the cell nucleus. But its shell is difficult to overcome. “This is a hurdle that complicates this technology,” says Watzl.
Thus, the Indian coronavirus vaccine is nowhere near as effective as mRNA vaccines, which provide over 95% protection against symptomatic coronavirus infection. In a registration trial involving 28,000 subjects, the ZyCoV-D vaccine achieved only 66% efficacy.
“However, the study was carried out when the delta variant of the coronavirus was already spreading in India,” Sander said. According to the manufacturer, ZyCoV-D also has extremely mild side effects, but the corresponding scientific data has not yet been published.
To improve the effectiveness of the vaccine, it is not injected into the muscle with a needle. It gets under the skin with a kind of vaccine “gun”.
However, the fact that vaccine DNA reaches the cell nucleus and is thus very close to human DNA raises concerns. At the very least, it can be assumed that the DNA of the vaccine is inserted into the human genome.
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