The three terms apply in slightly different ways to the same technique: building the body’s defences against specific diseases. Inoculation is the intentional introduction into the body (usually by injections which are often referred to as shots) of harmless bacteria or viruses to stimulate the production of natural disease-fighting substances known as antibodies. Vaccination strictly refers only to the introduction of smallpox vaccine into a scratch on the skin, but is often used more loosely to cover inoculation as well. Immunization is the term used for the process of providing ‘immunity’ (the protected state) by means of inoculation or vaccination. Repeated inoculations, called boosters, may be required at various times to stimulate by existing immunity against a specific disease.

2. The terms active immunity and passive immunity are often used. Do they mean the same things?

No, they don’t, and while the difference between them may be a bit complicated, it’s worth reviewing. Active immunity occurs when protective antibodies against a particular disease are made by the body. It can be acquired in two ways. You can develop the disease and then recover from it; or else you can be given a vaccine made from live or dead organisms.
Vaccination with live viruses that have been rendered harmless usually results in a mild form of the disease (you may not even know you have it), but one that still provides you with sufficient antibodies to produce what most scientists feel is lifetime immunity. Examples of such live vaccines include those for polio, rubella (German measles) and measles. Dead or inactivated vaccines, such as those for influenza, typhoid or cholera, also provide you with immunity but do not cause mild infection. In addition, they take longer to become effective than live virus vaccines.
Passive immunity, on the other hand, is acquired through the transfer of antibodies from a person who has active immunity against a specific disease to someone who does not. This can be done naturally, as in the case of a transfer from mother to foetus, or by inoculation, in which you actually receive antibodies for the particular disease being treated. For example, if you are exposed to someone who has infectious hepatitis B, you could receive injections of the hepatitis B immune globulin (HBIG). Immune globulins are special solutions of proteins made of antibodies drawn from human blood. Several types are available, including those for measles and hepatitis. In the case of HBIG, the antibodies are taken from patients who have had hepatitis B and have recovered from it. Thus they have developed their own natural active immunity. By receiving their antibodies, you will rapidly acquire a degree of protection against hepatitis B. if given early enough, HBIG can modify and even prevent development of the disease.
As a rule, passive immunity is less effective than active immunity. Because you have not had the disease or been vaccinated, the antibodies you receive provide only temporary protection.
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