Vaccination edu

When a healthy person becomes infected with a virus, eg. measles, the body recognises the virus as an invader, produces antibodies which eventually destroy the virus and recovery occurs. If contact with the measles virus occurs again in the future, the body’s immune system ‘remembers’ the measles virus and produces an increase in antibodies to destroy the virus.

Vaccination is the process that is used to stimulate the body’s immune system in the same way as the real disease would, but without causing the symptoms of the disease. Most vaccines provide the body with ‘memory’ so that an individual doesn’t get the disease if exposed to it.

Vaccination conveys immunity to diseases by a process called active immunity, which can be achieved by administration of either inactivated (ie. not live) or live attenuated organisms or their products. Live vaccines are attenuated, or weakened, by growing the organism through serial culturing (or passaging) steps in various tissue culture media. Inactivation is usually done using heat or formalin (sometimes both). Inactivated vaccines may include the whole organism (such as oral cholera vaccine), the toxin produced by the organism (such as tetanus and diphtheria vaccines), or specific antigens (such as Hib and pneumococcal vaccines). In some cases, the antigen is conjugated (ie. chemically linked) with proteins to facilitate the immune response. Inactivated viral vaccines may include whole viruses (such as IPV and hepatitis A vaccines) or specific antigens (such as influenza and hepatitis B vaccines). Live attenuated viral vaccines include MMR, rubella, varicella and yellow fever vaccines.

Immunity can also be acquired passively by the administration of immunoglobulins. Such immunity is immediate and is dose-related and transient. For example, measles or hepatitis B immunoglobulin can be used promptly after exposure in an unimmunised person to help reduce the chance of catching measles or hepatitis B from the exposure.