Immunization is a process of inducing immunity in people by administrating a biological substance containing either certain weakened or killed pathogen or its components. Such biological substances are called vaccines. The process of immunization has greatly reduced the mortality and morbidity rate of several diseases that were thought to be lethal in the past. Vaccines have proved to be a successful way to prevent serious infections including tetanus, influenza, measles, etc.
Though vaccines for many diseases are widely being used in almost every part of the world, still approximately 20 million children die annually due to a lack of access to vaccines.
Developing a successful vaccine against the pathogen is usually a complex and lengthy process that requires the involvement of both the public and private sectors. You may find this contradictory but the key component in the process of developing a vaccine is the weakened or unharmed form of the pathogen (bacteria or virus) against which the vaccine is being synthesized.
Path to develop a vaccine
According to the Centers for Disease Control (CDC), the process of vaccine development can be categorized into 6 major phases.
- Exploratory phase: It is the period when extensive research and study is conducted on the pathogen, its components, and replicative machinery which can be exploited for the synthesis of a vaccine.
- Preclinical phase: This phase determines the immunity generating potential of the candidate vaccine by administrating it to animal models and human tissue or cell cultures.
- The clinical phase: Clinical development phase is a point where a sponsor applies for the investigation of a new drug to the FDA. The application includes all the positive and negative research findings to date of the experimental vaccine. Once the application is verified by the FDA the vaccine undergoes human trials. These trials are subdivided into 3 phases.
- Regulatory review and approval: After successfully undergoing all three phases of human trials, the sponsor submits an application for a license for the administration of an experimental vaccine to patients.
- Manufacturing: The drug manufacturing industries go through every aspect from cost, equipment, labor to transportation, of making vaccines on a commercial scale.
- Quality control: The process of vaccine development does not end at the distribution of vaccines. The authorities are obliged to monitor the effectiveness and any adverse effects of the vaccine on the general public after its release.
Critical parameters in the development of SARS-Cov-2 Vaccine
Developing a vaccine for a novel pathogen like SARS-Cov-2 comes with great risks and uncertainty. The two parameters that measure success or risk of a vaccine are “biological uncertainty” and “execution uncertainties and risk”. Biological uncertainty refers to the natural potential of the vaccine to induce protective immunity in hosts that results in an affirmative risk-benefit ratio. Whereas, “execution uncertainties and risk”, refers to a positive outcome of every procedure that is designed to produce a vaccine.
In the vaccine developing process, safety and efficacy are the two most significant factors that determine the potential of the candidate vaccine to be used by the general public. Sometimes better efficiency of a vaccine comes with poor safety of the patients, i.e. number of side effects is greater than the benefit. As compared to efficacy, safety is given more value as therapeutic vaccines should be safe and healthy for the consumers.
It is crucial for the world to develop a vaccine for Coronavirus as soon as possible depending upon the same benefit-risk ratio. During a pandemic, a virus spreads at an insane speed that can only be reduced if herd immunity is developed in the community in the absence of a vaccine.
Many of you would be confused by the term herd immunity that defines a process in which a large population of the country becomes infected and is then recovered, resulting in natural immunity. Pakistan is considered to be moving towards herd immunity.
Approaches for Vaccine synthesis
A vaccine can be developed by using its component of the gene for the component or the weakened unharmed form of the whole pathogen. In the case of coronavirus, the component that is exploited is its spike proteins that are present on the surface of the virus. These spike proteins are responsible for the entry of the pathogen into the body cells of the host. Researchers are using genes for these spike proteins to formulate a vaccine most of which are at the clinical phase. Research is also being conducted on using the live attenuated form of coronavirus, its DNA, or other component proteins but it is difficult at this time to conclude which strategy would be more safe and successful.
Whether the vaccine for Coiv-19 would be developed after people will be immune to it?
Vaccine development is a lengthy process that can take almost a decade from its synthesis in the lab to be released in public. So, it would be unjust to expect a vaccine for Covid-19 before the end of even 2021. Still, it would be a great success if the scientists and manufacturers would be able to make a vaccine that quick, considering the normal time period of development. The factors that are helping to fasten the vaccine development procedure for Covid-19 are genetic and protein engineering, computational biology, antigen design based on the structure of the pathogen, etc.
What to expect?
What is making the development of the vaccine most difficult is the mutation that is occurring in coronavirus. These mutations make the pathogen-resistant, resulting in the failure of a number of vaccines. Along with the benefits, trials are also being conducted to assess disease enhancement that can be caused by a vaccine.
Companies are making vaccines development process swift by running side by side experiments on multiple species of animals. This can give insight into the pros and cons of the vaccine at an early stage.
Production of the Covid-19 vaccine at a global scale in a short time period is a challenging task but manufacturers are enthusiastic about it.