A vaccine is a biological preparation that provides active acquired immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins or one of its surface proteins. The agent stimulates the body’s immune system to recognize the agent as a threat, destroy it, and keep a record of it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters
Vaccines have historically been the most effective means to fight and eradicate infectious diseases. Limitations to their effectiveness do exist. Sometimes, protection fails because the host’s immune system doesn’t respond adequately or at all. Lack of response commonly results from clinical factors such as diabetes, steroid use, HIV infection or age. However it also might fail for genetic reasons.
Adjuvants commonly are used to boost immune response, particularly for older people (50–75 years and up), whose immune response to a simple vaccine may have weakened.
Vaccines are dead or inactivated organisms or purified products derived from them.
There are several types of vaccines in use. These represent different strategies used to try to reduce risk of illness, while retaining the ability to induce a beneficial immune response.
Some vaccines contain inactivated, but previously virulent, micro-organisms that have been destroyed with chemicals, heat, radioactivity, or antibiotics. Examples are influenza, cholera, bubonic plague, polio, hepatitis A, and rabies.
Some vaccines contain live, attenuated microorganisms. Many of these are active viruses that have been cultivated under conditions that disable their virulent properties, or that use closely related but less dangerous organisms to produce a broad immune response. Although most attenuated vaccines are viral, some are bacterial in nature. Examples include the viral diseases yellow fever, measles, rubella, and mumps, and the bacterial disease typhoid.
The infographic above from Compound Interest shows the common components of vaccines.
When making vaccines, antibiotics can be used to prevent bacterial contamination. Although these are removed after manufacture, trace amounts can still remain in the final vaccine. Antibiotics that often cause adverse allergic reactions, such as penicillins, are avoided, in favour of antibiotics such as gentamycin and neomycin.
For more information visit:-
via Blogger http://ift.tt/1Aulwvv