Vaccination is the administration of a vaccine to help the immune system develop protection from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. In stimulating the body’s adaptive immunity, they help prevent sickness from an infectious disease.
When a sufficiently large percentage of a population has been vaccinated and become immune, herd immunity results which indirectly protects the non-immune population because infection transmission is low. The effectiveness of vaccination has been widely studied and verified. Vaccination is a most effective method of preventing infectious diseases.
Vaccination and immunization have a similar meaning in everyday language. This is distinct from inoculation, which uses unweakened live pathogens.
Germs can be viruses (such as the measles virus) or bacteria (such as pneumococcus). Vaccines stimulate the immune system to react as if there were a real infection. It fends off the “infection” and remembers the germ. Then, it can fight the germ if it enters the body later.
There are 4 main types of vaccines: Live-attenuated vaccines, recombinant, polysaccharide, and conjugate vaccines
Antibodies are specific to each individual disease. Having antibodies to measles does not protect you from catching mumps or chicken-pox, etc.
Active and passive Immunization
Active immunization: this happens by being exposed to a disease causing organism, either by catching it in the normal way or through vaccination with a dose of the responsible virus or bacteria which has been killed or inactivated. This is usually long lasting. It may take some time to fully develop and often needs ‘boosting’.
Passive immunization: this is a way of giving immediate immunity by injecting already existing antibodies (from someone else) into a person who has just been, or may shortly be, exposed to a particular infection. Passive immunity is immediately effective, but doesn’t last for long.
Childhood immunization: The creation of immunity through vaccination is usually started at birth. Different countries have different immunization schedules based on global and national prevalence.
Adult immunization: As well as being of vital importance in childhood, vaccination is also essential for adults. Some are boosters from childhood vaccines while others are travel vaccines required when going to a country with different infection prevalence.