There are several diseases like Diphtheria, whooping cough (pertussis), measles, mumps, Yellow fever, small pox and German measles (rubella) that are unfamiliar to many these days. However, in the 19th and early 20th centuries, these illnesses struck hundreds of thousands of people worldwide and among these most were children. These illnesses killed tens of thousands of people. Today these diseases are all but forgotten. This change has happened largely because of vaccines.
The term ''vaccine'' was derived from the Edward Jenner's 1796 use of the term ''cow pox'' (Latin ''variolæ vaccinæ'', adapted from the Latin ''vaccīn-us'', from ''vacca'' cow). He was the pioneer of using cow pox vaccines to prevent small pox infections.
Vaccines and the immune system
When an individual is vaccinated against a disease or an infection, say Diphtheria, his or her immune system is prepared to fight the infection. Once vaccinated when the person is exposed to the bacterium that causes it the body gears up to fight off the infection. This whole battle of the immune system with the invading bacterium is so rapid that most people do not observe or feel the infection at all.
Vaccines take advantage of the body’s natural ability to learn how to eliminate almost any disease-causing germ, or microbe, that attacks it. Once vaccinated the body “remembers” how to protect itself from the microbes it has encountered before.
What are vaccines made of?
A vaccine is a biological preparation that improves immunity to a particular disease. Traditional vaccines contain either parts of microbes or whole microbes that have been killed or weakened so that they don’t cause disease.
When a person is inoculated with these preparations, the immune system confronts these harmless versions of the germs. The immune system quickly clears them from the body.
In turn the body remembers the germs so that later in life when it encounters the real live virulent germs it may be able to fight it off with the retained memory against the particular germ.
Types of vaccines
Some vaccines are prophylactic and are used to prevent or ameliorate the effects of a future infection by any natural or "wild" pathogen. Some vaccines however may also be therapeutic for example cancer vaccines that are being developed against cancer.
Once a person’s immune system is trained to resist a disease, the person becomes immune to it. Before vaccines, the only way to become immune to a disease was to actually get it and, with luck, survive it. This type of immunity against an illness is called naturally acquired immunity, wherein the person has to suffer the symptoms of the disease and also risk the complications, which can be quite serious or even deadly. In addition, if the disease is contagious it may also be passed on to family members, friends, or others who come into contact.
Vaccines, which provide artificially acquired immunity, are a much safer way to become immune. Vaccines can prevent a disease from occurring in the first place and also decrease the risk of complications and risk of transmission. It is much cheaper to prevent a disease than to treat it.
Until recently, most vaccines were aimed at babies and children alone. Now more and more vaccines are developed for use among elderly, pregnant mothers, adolescents, travellers and adults in a population.
In addition, vaccines are increasingly being administered in form of combination of more than one component. Vaccinations of animals are being used both to prevent their contracting diseases and to prevent transmission of disease to humans.