12th Class Biology Microbes in Human Welfare Vaccines

History of Vaccines and Vaccination : In vaccination weakened or dead pathogens, or portions of pathogens, are injected into a person who is required to be made immune. The pathogens given in a vaccine are unable to cause the disease, but are sufficient to stimulate the formation of antibodies by host’s cells. The process of vaccination was initiated by Edward Jenner in 1790. He observed that milkmaids did not contract smallpox apparently because they were exposed to a similar but milder form of disease called cowpox. Edward Jenner infected first James Phipps,, a healthy boy of about 8 years with cowpox and two months later he infected the boy with smallpox. The boy did not suffer from small pox. Jenner proposed that an induced mild form of a disease would protect a person from a virulent form (which has ability to damage the host). He used the term vaccine (in Latin Vacca means ‘cow’) and the term vaccination for protective inoculation. Edward Jenner was the first to discover a safe and effective means of producing artificial immunity against small pox. Thus once vaccination is done the individual is protected from the disease. Vaccination develops acquired immunity. Pasteur confirmed Jenner’s findings and produced vaccines for other diseases like anthrax, rabies and chicken cholera.

For protection need : Antibody provoking agents are called vaccines. These are used against viral and bacterial diseases. Calmette & Guerin developed BCG vaccine for T.B. and Salk made Polio vaccine. Sabin also prepared Polio vaccine. Enders developed vaccine against measles. WHO was formed in 1948 at Geneva to take health problems at global level. In May, 1974, Global Immunisation Programme was launched by WHO for six disease (Diphtheria, Pertussis, Tetanus, Measles, TB & Polio).

Vaccination : It is the possible way to induce active acquired immunity against the germs of various diseases such as polio, diphtheria, whooping cough, tetanus and small pox. The immune system is thus induced to produce antibodies against these antigens. The artificial introduction of disease factors in the body is known as vaccination. Usually 2-3 injections are given to achieve full immunity against a specific pathogen and the further dose is called as booster doses.

Other Vaccines : Vaccines are also available for diphtheria, tetanus, whooping cough, tuberculosis, measles, polio, mumps, plague.

Types of Vaccines

(1) Killed vaccine : These vaccines are prepared by killing the pathogenic organisms by heat uv-rays/alcohol formalin/phenol, e.g., Typhoid Vaccine, Cholera Vaccine.

(2) Toxoid : These are prepared by destroying the toxic property of the toxins produced by organisms but retaining its antigenic property, e.g., Tetanus toxoid, Antidiphtheria toxoid.

(3) Attenuated living vaccines : The pathogen is made weakened to make it nonvirulent, e.g., Oral Polio Vaccine (OPV), BCG (Bacille Calmette Guerin). MMR (Mumps, Measles, Rubella) Provide active life long immunity.

(4) Antibodies as vaccines : Serum is used after a person/animal has been exposed to infection. This serum contains antibodies against that pathogen. It provides passive artificial immunity for some period only, e.g., ATS (Anti tetanus serum), Antirabies serum.

(5) Antigens like polysaccharides of Pneumococci, Interferon (glycoproteins) are also used as vaccines.

Some Important Vaccines