WHAT IS A VACCINE?
A vaccine is a biological preparation that mimics a natural infection and leads to the development of immunity similar to that acquired by the body during the first contact with a real microorganism (i.e. a bacterium or a virus ). Vaccines contain live or killed microorganisms (bacteria or viruses), their inactivated toxins, or fragments of killed microorganisms incapable of causing disease, which when introduced into the body induce the development, after a certain time, of an immunity directed precisely against the pathogenic agents.
Vaccinations produce immunity against specific viruses or bacteria, preventing people from getting sick and spreading the infection to each other. They thus limit the spread of diseases – Look here: homepage.
TYPES OF VACCINES
Several types of vaccines are currently in use. They are classified in several ways: for example, according to the type of microorganism combated (viral and bacterial or mixed vaccines), the mode of administration (injectable, oral, intranasal) or the extent of the immunological action (specific and non-specific). However, the most important division to keep in mind is that of vaccines according to the nature of the antigens.
Attenuated vaccines contain live bacteria and viruses that cannot cause disease. Live-attenuated virus vaccines inject a live version of the germ or virus that causes the disease into the body. Although the germ is a living specimen, it is a weakened version that does not cause any symptoms of infection as it is unable to replicate once inside the body. Vaccines containing live attenuated virus induce an immune response similar to that which would occur during a natural infection, but the person is unable to transmit the virus to others and will not become ill with illness caused by the virus .
Inactivated vaccines contain killed bacteria, viruses or their fragments. An inactivated vaccine uses a strain of bacteria or virus that has been destroyed by chemical means or radiation. This dead version of the virus or bacteria is then injected into the body. They do not induce an immune response as strong as that induced by live attenuated vaccines.
Toxoid vaccines contain specially formulated inactivated bacterial toxins that cause specific diseases. Toxoid vaccines use toxins produced by bacteria or viruses to create immunity against specific parts of the bacteria or virus causing the disease, rather than against the bacteria or virus as a whole. The immune response focuses on that specific toxin.
Recombinant vaccines are a new generation of vaccines, obtained by genetic engineering. Recombinant vaccines are created by incorporating a fragment of the microorganism’s genetic material into mammalian or yeast cells. The genetically modified (recombinant) cells begin to produce a new protein which, when isolated and purified, becomes the vaccine antigen.
Another division of vaccines that every patient should be aware of is content:
– Single-component (monovalent) vaccines provide immunity against a single infectious disease. They may contain a single type of microorganism or antigens from a single microorganism.
– Multicomponent (polyvalent) vaccines contain several types of the same microorganism or antigens of several types of the microorganism.
– Combined vaccines make it possible to simultaneously immunize the body against several infectious diseases. They contain several microorganisms or antigens derived from several microorganisms.
– Highly combined vaccines reduce the number of injections given, which reduces pain and stress for the child and limits the risk of infection during vaccination.