By| Published: April 22nd, 2017
Have you pondered over a thought that the future generations would be free of most diseases? Diseases like smallpox that once upon a time killed thousands!
Even before the modern era of immunization began, the practice dates back hundreds of years.
What is immunization?
Immunization is a process involving the use of vaccines to help prevent diseases that can cause illness, disability or death.
Vaccine is a suspension of attenuated or killed micro-organisms (bacteria, viruses, or rickettsias) or derivative antigenic (e.g. proteins or peptides) that is transferred to a non-exposed individual to confer immunity to the disease.
How did immunization come into existence?
The history of vaccination dates to the 7th century, where some Indian Buddhists used to drink snake venom in order to become immune to its effect. Simultaneously according to our historic records, a Hindu physician named Dhanwantari is said to have performed vaccination against Smallpox in the seventh century.
The procedures of vaccination testing have been experiment worldwide. An 18th century documentation of Chinese variolation, called as “The Golden Mirror of Medicine”, listed three forms of inoculation against smallpox which used to be a common disease throughout the world.
After years of experimentation, Dr. Edward Jenner inoculated a boy named James Phillip. Jenner’s experiment was a success as the boy did not contract with smallpox. He submitted his findings to the Royal Society in 1790s and created the science of immunology.
With Rabies, Anthrax and much more infectious diseases that were affecting the human race, in 1885 a French chemist Louis Pasteur developed vaccines for Anthrax and Rabies. In the early 20th century, the chemical inactivation of diphtheria and other bacterial toxins led to the development of the first toxoids: diphtheria and tetanus. BCG (Bacille Calmette-Guerin), the vaccine against tuberculosis, was the first live vaccine for humans to be produced since Pasteur’s rabies vaccine. In 1906, Calmette and Camille Guerin started sub culturing a strain of mycobacterium. After 13 years of attenuation by 230 passages in beef bile, potatoes and glycerol, the strain eventually became the BCG strain.
Notable achievements in the progress of immunization availability:
- In 1927, Clinical Trials were conducted on children and the vaccine became available for human for use in 1927. Controlled clinical trials were conducted from 1923 to 1929 by Thorvald Madsen and several whole-cell Pertussis vaccines were in use by the late 1940s. The first combination vaccine, Diphtheria Pertussis Toxoid (DPT), became available in 1948.
- The polio vaccine, developed with a variant virus strain grow in mice, was tested on humans in 1950 by Hilary Koprowski.
- The first licensed product developed using the cell culture technique of Enders, Weller and Robbins was the trivalent, formalin-inactivated polio vaccine of Jonas Salk. Later in 1960, Albert Sabin’s live attenuated polio vaccine was licensed in the U.S. which is now commonly known as the Oral Polio Vaccine (OPV).
What are the types?
Vaccines are generally classified based on the type of preparation employed for their production. The different types of vaccines are as follows:
- Live, weakened (attenuated) vaccines: Vaccines for Polio (Sabin vaccine), Measles Mumps Rubella (MMR) and Chickenpox are best examples of live attenuated vaccines. The benefit of this type of vaccines is that it produces a strong response and a life-long immunity with 1-2 doses. However, it is considered unsafe for immunocompromised people.
- Inactivated or killed vaccines: Vaccines for Polio (Salk vaccine), Hepatitis A, Rabies, Cholera and Flu are best examples of inactivated or killed vaccines. These vaccines are considered safe for people who have compromised immune system. This type of vaccine does not provide lifelong immunity as compared to live attenuated vaccines. However, booster doses are required every few years for effectiveness.
- Subunit vaccines: Hepatitis B is a subunit vaccine and rarely is known to cause any adverse reaction. High level of purification is required to produce such vaccines, and this may lead to loss of immunogenicity.
- Conjugate vaccines: Haemophilus Influenza B (Hib) and Pneumococcal vaccine are conjugate vaccines. They are safe for immunocompromised people and booster shots are required to maintain its effectiveness.
- Toxoids derived from bacterial toxins: Tetanus Toxoid is derived from bacterial toxin tetanospasmin, which is produced by Clostridium tetani. This type of vaccine also requires a booster dose.
Immunization is one of the most beneficial public health measure of all times, where the government, non-governmental and other agencies are working in tandem to develop safe and effective vaccines. There is a remarkable track record improvement in the way diseases are being dealt as of today, particularly if we consider the serious nature of the diseases. Pledge yourself a healthy and disease-free life. A conscious decision is all that is needed for a healthy life, because American humourist Josh Billings once said, “Health is like money, we never have a true idea of its value until we lose it”.