ZyCov-D vaccine, the world’s first DNA vaccine

Context:

Ahmedabad-based ZydusCadila has applied to Central Drugs Standard Control Organisation (CDSCO), the national drugs regulator, seeking emergency use authorization (EUA) for ZyCov-D, its Covid-19 vaccine. If approved by the regulator, ZyCov-D will be the world’s first DNA vaccine against infection with SARS-CoV-2.

What is the ZyCov-D vaccine or DNA vaccine?

• ZyCov-D is a “plasmid DNA”. This DNA is engineered to show the desired results.
• The plasmids used in the vaccine are coded with the instructions to make the spike protein of SARS-CoV-2.
• Vaccination gives the code to cells in the recipient’s body, so they can begin making the spiky outer layer of the virus.
• The immune system is expected to recognize this as a threat and develop antibodies in response.
• No needle is used to deliver the vaccine, instead, a spring-powered device delivers the shot.
• ZyCov-D has been developed with the support of the central government’s Department of Biotechnology and the Indian Council of Medical Research (ICMR).

Plasmid

• A plasmid is a small, circular, double-stranded DNA molecule that is distinct from a cell’s chromosomal DNA.
• Plasmids naturally exist in bacterial cells, and they also occur in some eukaryotes.
• Often, the genes carried in plasmids provide bacteria with genetic advantages, such as antibiotic resistance.

Safety concerns

Safety concerns to integrate into cellular DNA or cause auto-immune diseases.

Emergency Use Authorization

• In the current pandemic situation, it may not be possible to have all the evidence that a drug regulator would normally require for approving a drug, vaccine, device, or test.
• When there is a declared emergency, the regulator, in India’s case the DCGI, can take a call whether it is worth releasing a drug or vaccine that is not fully tested for efficacy and safety.
• If there is evidence to suggest it may benefit patients, then the regulator is well within its rights to issue an emergency use authorization to a medical product to make it widely available for use.

Vaccines approved under the EUA

• The process for using the EUA is less clearly spelled out in India, but the DGCI has also been issuing EUAs based on clinical trial data.
• In January, the DCGI approved the first two vaccines
• Covishield, produced by Pune-based Serum Institute of India under licensing agreement from AstraZeneca
• Covaxin, manufactured by Bharat Biotech.