- Sputnik V, developed by Gamaleya Research Institute of Epidemiology and Microbiology,
- is a two dose adenovirus based vector vaccine, similar in design to AstraZeneca’s Covishield.
- A challenge with the vaccine is its storage. The liquid form of the vaccine requires it to be stored at 18°C or colder while the freeze dried version can be stored in 28°C. The company was asked by the regulator to furnish more information on the cold storage management plan and its stability.
Adenovirus Vector Vaccine :
- In this vaccine, adenovirus is used as a tool to deliver genes or vaccine antigens to the target host tissue.
- Adenovirus: Adenoviruses (ADVs) are DNA viruses ranging from 70-90 nanometre in size, which induce many illnesses in humans like cold, respiratory infection etc.
- Adenoviruses are preferred for vaccines because their DNA is double stranded which makes them genetically more stable and the chances of them changing after injection are lower.
- Rabies vaccine is an adenovirus vaccine.
- However, there are drawbacks of adenovirus vector vaccines like pre-existing immunity in humans, inflammatory responses etc.
- Just as human bodies develop immune responses to most real viral infections, they also develop immunity to adenoviral vectors. Since adenoviral vectors are based on natural viruses that some humans might already have been exposed to, these vaccines might not work for everyone.
Development of a vaccine
- The general stages of the development cycle of a vaccine are:
- Exploratory stage
- Pre-clinical stage
- Clinical development
- Regulatory review and approval
- Manufacturing and
- Quality control.
The Clinical development is a three-phase process:
- Clinical trials in humans are classified into three phases: phase I, phase II and phase III and in certain countries formal regulatory approval is required to undertake any of these studies.
- The phase I clinical studies carry out initial testing of a vaccine in small numbers (e.g. 20) of healthy adults, to test the properties of a vaccine, its tolerability, and, if appropriate, clinical laboratory and pharmacological parameters. Phase I studies are primarily concerned with safety.
- Phase II studies involve larger numbers of subjects and are intended to provide preliminary information about a vaccine’s ability to produce its desired effect (usually immunogenicity) in the target population and its general safety.
- Extensive phase III trials are required to fully assess the protective efficacy and safety of a vaccine. The phase III clinical trial is the pivotal study on which the decision on whether to grant the licence is based and sufficient data have to be obtained to demonstrate that a new product is safe and effective for the purpose intended.
- Many vaccines undergo Phase IV formal ongoing studies after the vaccine is approved and licensed.