The COVID-19 vaccines that a large part of the population of the most developed countries have already received are of two types: messenger RNA (Pfizer and Moderna) or vector-based (Janssen and AstraZeneca). However, many scientists are working to develop another type of vaccine, and even the first one has already been approved in India for emergency use. It’s about DNA vaccines.
In particular, this vaccine, from the manufacturer Cadila Healthcare, has been baptized as ZyCoV-D, and is administered without the need for a needle (with a disposable injector) in three doses.
What are DNA vaccines?
The most popular messenger RNA (mRNA) vaccines, such as Pfizer and Moderna, use these molecules, which are naturally found in the body and are vital in gene expression, as ‘instructions’ for the body to make certain proteins. Essential to provoke an immune reaction that protects from the virus. DNA vaccines work in a similar way , using human DNA to provide the body with the same information.
The development of this technology is the result of the discovery, some three decades ago, that it was possible to achieve the expression of a given gene by direct injection of a naked DNA fragment.
However, DNA vaccines have some added difficulties in their mechanism of action. First, that the injection must be direct into a cell, and not into the bloodstream. On the other hand, DNA vaccines that have been used to date (in animals, although they have also been previously tested in humans) have produced less strong and long-lasting immunities .
And indeed, this appears to be the case for ZyCoV-D as well, which has so far shown 66% efficacy against symptomatic disease and is likely to offer less durable protection than mRNA or vector vaccines.
What advantages do they offer?
However, these drawbacks do not invalidate the potential uses of this technology. DNA vaccines offer some advantages over the other types that can be very useful , especially in the current phase of the pandemic.
And it is that DNA vaccines are cheaper, are safe and are more stable than their counterparts.
For example, the manufacturer has indicated that the serum is stable at 25º for three months, which facilitates its transport and storage in areas with fewer resources, where the current vaccination rate is also lower than that of more developed countries.
This is why the approval of the vaccine by India is for emergency use. Although it is preferable to administer an mRNA or vector vaccine if possible, the DNA vaccine can help stop the transmission of the virus in a country that so far has only 13% of its adult population fully vaccinated , or in others in those for which the rate is even lower due to economic and logistical difficulties.