The process of vaccine development lasts for a minimum of 10- 15 years and needless to say, it is a very complex process. Of all the candidates selected for development, only a tiny percentage makes it to the final licensing state, which makes the process of vaccine development extremely expensive. Vaccine development involves a combination of public and private efforts.
By the end of the 19th century, a plethora of vaccines were developed in the United States against diseases like smallpox, rabies, plague, cholera etc. but there was no known regulation of vaccine development. In the year 1902, the US congress passed the Biologics Control Act to control the quality of drugs which established the government’s right to control the establishments were vaccines developed and produced. In the EU, the EMA (European Medicines Agency) supervises the regulation of vaccines and all other drugs.
Vaccine development can be broadly classified into 2 different categories namely the – Pre Clinical Development and the Clinical Development. Prior to the Pre Clinical Development, there are basic laboratory research involved, lasting for a span of 2-4 years wherein researchers try to identify natural or synthetic antigens that might help prevent diseases. These antigens are primarily derived from pathogens in the form of weakened strains of bacterial toxins, virus like particles or weakened viruses or bacteria. Pre- Clinical development focuses primarily in conducting research on animals. The goals of this phase are to screen antigens, conceptualize the vaccine and evaluate the vaccine efficacy in animals and test tube assays. These studies are never conducted in humans. And many of the candidate vaccines never progress beyond this stage as they fail to entice a proper immune response. This stage lasts for a year or two.
If a vaccine shows a satisfactory result in the above stage, an Investigational New Drug (IND) application is then submitted to the US FDA wherein the sponsor describes the manufacturing process, summary of laboratory findings etc. in details and proposes a study in the form of a protocol. The FDA takes 30 days time to approve this application, upon which the vaccine development progresses to the next step.
The next stage of vaccine development progresses in humans and is often known as the Clinical Development Phase. This Phase covers the initial trials in humans (Phase 1) right through introduction and then beyond (Phase IV). Phase 1 is relatively small scale and checks the immune response of the vaccine in humans. This phase also outlines the safety of the vaccine in humans. Phase II trials are usually larger and mainly look to determine the efficacy of the vaccine against infections and clinical diseases. Side effects of the immune response evoked and the general safety of the vaccine is also studied in this phase. Vaccines that progress to Phase III are being subjected to a large scale population across multiple locations to prove the efficacy of it under real time disease conditions. This helps the manufacture to market the vaccine as they can apply to regulatory agencies for a license to market the product for human use. Phase IV is also known as post marketing surveillance which aims to detect adverse events which may occur rarely even after marketing the vaccine.