Immunization is a process of developing resistance to infections by administration of antigens or antibodies. Inoculation of vaccines into the body to prevent diseases is called as vaccination.
One effective way of controlling the spread of infection is to strengthen the host defenses. This is accomplished by immunization, which is one of the cost effective weapon of modern medicine.
When a large proportion of a community is immunized against a disease, the rest of the people in the community are benefited because the disease does not spread.
Vaccines are preparation of living or killed microorganisms or their products used for prevention or treatment of diseases. Vaccines are of two types: Live vaccines and Killed vaccines
They are prepared from living organisms.
The pathogen is weakened and administered.
e.g. BCG vaccine, oral polio vaccine.
Micro organisms (bacteria or virus) killed by heat or chemicals are called killed or inactivated vaccines. They require a primary dose followed by a subsequent booster dose. e.g. Typhoid vaccine, cholera vaccine, pertussis vaccine.
The World Health Organization in the year 1970 has given a schedule of immunization for children. This schedule is carried out in almost all countries. The immunization schedule indicates the age at which the vaccine should be administered to protect the children from infectious diseases. Table 8.8 gives the schedule of vaccination procedures followed in India.
BCG (Bacillus Calmette Guerin): This was prepared by two French workers Calmette and Guerin (1908-1921). It was developed for over a period of thirteen years. The bacilli are weakened and used for immunization against tuberculosis.
DPT (Triple Vaccine): It is a combined vaccine for protection against Dipetheria, Pertussis (whooping cough) and Tetanus.
MMR: Mumps, Measles, Rubella vaccine gives protection against viral infections.
DT: It is a dual antigen or combined antigen. It gives protection from Diphtheria and Tetanus. (Tetanus Toxoid): Toxin of Tetanus bacteria.
TAB: Combined vaccine for typhoid, paratyphi A and paratyphi B.