May 28, 2022

Vaccine (from Latin vaccinus - “cow”, colloquial “vaccination”) is a medical preparation of biological origin that provides the body with the appearance of acquired immunity to a specific antigen. The vaccine usually contains an agent that resembles the disease-causing microorganism and is often made from a weakened or killed form of the microbe or one of its surface proteins. Drugs made from toxins produced by microorganisms are called toxoid (not a vaccine). The agent stimulates the body's immune system to recognize the agent as a threat, destroy it, and further recognize and destroy any microorganisms associated with that agent that it may encounter in the future. Vaccines may be prophylactic (to prevent or reduce the effects of future infection with a natural or wild pathogen) or therapeutic (eg, curative brucellosis vaccine, cancer vaccines under investigation). The introduction of a vaccine into the body is called vaccination. According to the definition given by the World Health Organization (WHO), “vaccination is a simple, safe and effective way to protect against diseases before a person comes into contact with their pathogens. Vaccination activates the body's natural defense mechanisms to build resistance to a range of infectious diseases and makes your immune system stronger." Vaccination is the most effective method of preventing infectious diseases. Widespread immunity through vaccination is largely responsible for the worldwide eradication of smallpox and the limitation of diseases such as polio, measles, and tetanus in most parts of the world. People's lack of confidence in vaccination is listed as one of the top 10 health problems that WHO worked on in 2019. WHO estimates that immunization prevents 2 to 3 million deaths each year. It is one of the most cost-effective types of investment in health care. It is technically possible to prevent an additional four million deaths each year.

Phases of vaccine development and testing

Vaccine development �