How vaccines are developed

The development of a new vaccine follows the general stages as for other drugs and other biological agents. In the exploratory and pre-clinical stages, a company that wishes to develop a vaccine first describes the vaccine, how it will be manufactured, the quality control tests to be done, the vaccine’s safety and ability to elicit a protective immune response or immunogenicity in animal testing, and the proposed clinical protocol for studies in human beings. Clinical trials are then done in humans and these trials typically go through three phases:
Phase 1. Safety, efficacy (immunogenicity) or serious side effects are observed in 20 to 200 volunteers.
Phase 2.Vaccine is given to several hundreds of subjects with characteristics like age, gender, and physical health similar to people to whom the vaccine is intended. Efficacy and safety are monitored. Common short-term side effects are observed.
Phase 3.Trials are expanded to enroll hundreds or thousands of volunteers to provide the critical documentation of effectiveness and important additional safety data required for licensing. Researchers compare the response of people who get the vaccine with the response of people who did not get the vaccine.
Phase 4.Formal or ongoing studies are done in many vaccines even after it is licensed and approved for use by the Food and Drug Administration or licensing body of the country where the vaccine is being developed. These studies continue to monitor safety, efficacy, and other aspects of the vaccine.
The development of any vaccine may be stopped at any stage of its development if significant data show that it is not effective or protective or if there may be adverse side effects. Efficacy and safety information necessary to make a risk/benefit assessment and to recommend or oppose the approval of a vaccine are required. Pre-approval inspections during production of the vaccine are conducted.
Vaccine approval also requires an adequate product labeling to allow health care providers to understand the vaccine’s proper use. This includes potential benefits and risks, means of communication with patients, and safe delivery of the vaccine to the public.
Numerous vaccines are being developed for the prevention of the Covid-19. The candidate vaccines differ in their potential safety and immunogenicity, cost of manufacturing, and speed of development. In early trials, some vaccines have led to the production of anti-bodies in healthy adults. In non-human subjects (monkeys), there was more rapid clearance or lower levels of the virus in vaccinated groups compared with non-vaccinated groups.
It has also been suggested that immunization with Bacille-Calmette-Guerin (BCG) vaccine (intended for protection against tuberculosis) may lead to the production of protective immune response against viral infections. Further studies are being done to assess the impact of BCG immunization in relation to coronavirus infection.
Clinical studies are being done in several countries to test the efficacy and safety of drugs or other interventions, like monoclonal anti-bodies that may neutralize the coronavirus or agents that may prevent Covid-19 infection. No drug or intervention is known yet to be effective in preventing infection after exposure to Covid-19 positive cases.
Also, no drug or intervention has been shown to be effective in preventing infection or as primary prophylaxis. Physical distancing, maintaining good health, and proper disinfection procedures remain the mainstay of prevention.
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