Sputnik V, the Russian-developed Covid-19 vaccine, has recently been granted emergency use by the Drugs Controller General of India (DCGI). This approval marks it as the third coronavirus vaccine allowed for emergency use in the country, following Covishield, developed by the Serum Institute of India and Covaxin, developed by Bharat Biotech.
Development and Mechanism of the Sputnik V Vaccine
Sputnik V was created by the Gamaleya National Research Institute of Epidemiology and Microbiology in Moscow. The vaccine’s mechanism involves using two distinct adenoviruses – which are common cold-causing viruses in humans – that have been weakened so they can’t replicate within a human body or cause any disease.
Moreover, these adenoviruses have been modified to deliver a code that produces the coronavirus spike protein. The goal is to prepare the body to create an immune response in the form of antibodies when the real virus attempts to infect the body.
The Distinct Features of Sputnik V
One of the unique features of Sputnik V is the usage of different vectors for each of the two shots given throughout the vaccination course. This method results in a more durable immunity compared to vaccines that use the same delivery mechanism for both shots. The two shots are administered 21 days apart.
The storage requirement of Sputnik V varies based on its form. In its liquid state, it necessitates storage at -18°C, while in its freeze-dried form, it can be stored at 2-8°C. This means it can be kept in a conventional refrigerator without needing additional cold-chain infrastructure.
Efficacy and Trials of Sputnik V
Phase 3 trials were carried out in Russia, and the results, published in The Lancet, revealed an efficacy rate of 91.6%. In India, Dr Reddy’s conducted a bridging study prior to applying for emergency use approval. The trial participants were given the first dose (rAd26-), followed by a booster (rAd5-S) after 21 days.
Understanding Adenoviruses
Adenoviruses (ADVs) are DNA viruses with a size ranging from 70-90 nanometres. They can induce various illnesses in humans, including colds and respiratory infections. ADVs are often selected for vaccines because their DNA is double-stranded, making them genetically more stable and reducing the likelihood of changes post-injection.
A notable example of an adenovirus-based vaccine is the rabies vaccine. Adenovirus vaccines fall into the category of viral vector vaccines wherein the adenovirus is employed as a tool to deliver genes or vaccine antigens to the target host tissue.
However, adenovirus-based vaccines do have some drawbacks. These include pre-existing immunity in humans, which could cause inflammatory responses. Like with most real viral infections, bodies also develop immunity to adenoviral vectors. Since these vectors are based on natural viruses to which some humans may already have been exposed, these vaccines may not be effective for everyone.
