Injection

In medical care, an injection is the introduction of a drug, vaccine, contraceptive or other therapeutic agent into the body using a needle and syringe. Injections are among the most common health care procedures throughout the world. 

It is of vital importance that injections are carried out safely, i.e. in a way that does not harm the patient or expose the health care worker to unnecessary risk, and does not result in waste that is dangerous for the community. The use of sterile equipment for all injections is essential. An injection (often referred to as a "shot" in US English, or a "jab" in UK English) is an infusion method of putting fluid into the body, usually with a syringe and a hollow needle which is pierced through the skin to a sufficient depth for the material to be administered into the body. An injection follows a parenteral route of administration; that is, administration via a route other than through the digestive tract. Since the process

inherently involves a small puncture wound to the body (with varying degrees of pain depending on injection type and location, medication type, needle gauge and the skill of the individual administering the injection), fear of needles is a common phobia.

There are several methods of injection or infusion used in humans, including intradermal, subcutaneous, intramuscular, intravenous, intraosseous, intraperitoneal, intrathecal, epidural, intracardiac, intraarticular, intracavernous, and intravitreal. Rodents used for research are often administered intracerebral and intracerebroventricular injections as well. Long-acting forms of subcutaneous/intramuscular injections are available for various drugs, and are called depot injections.

Injections are among the most common health care procedures, with at least 16 billion administered in developing and transitional countries each year. 95% of injections are administered in curative care, 3% are for immunization, and the rest for other purposes, such as blood transfusions.^[1] In some instances the term injection is used synonymously with inoculation even by different workers in the same hospital. This should not cause confusion; the focus is on what is being injected/inoculated, not the terminology of the procedure.

Sources: WHO.int
               wikipedia.org