When an individual encounters a disease causing antibody, the individual’s immune system produces a defense against it. These defensive bodies are called antibodies. There are specific types of antibodies to tackle and eliminate specific antigens. With every consecutive attack of a known antigen, the body launches a swifter and more efficient attack to eradicate the antigen even before the first signs of a disease develop. The immune system is capable of tackling hundreds of thousands of different micro-organisms.
While designing a vaccine, various factors have to be kept in mind. These are factors like the type of the microbe being used, its characteristics, its style of manifestation and physicals factors like the region within which the vaccine is to be used. Based on such factors, vaccines are of the following types.
Attenuated Vaccines: In this type of vaccines, a weakened version of the microbe is used against which the immunization is sought. This type of vaccine is the closest to a live infection, triggering a strong antibody response that may ensure lifelong immunity. The Oral Polio Vaccine (OPV), Measles and Varicella vaccines are attenuated vaccines.
Inactivated Vaccines: In this type of vaccines, disease-causing microbes are killed before the vaccine is prepared. They are safer than attenuated vaccines but weaker in response and thus, may need more than one dose to prolong immunity. An example is the Inactivated Polio Vaccine (IPV).
Subunit Vaccines: This type of a vaccine employs a certain part of the microbe and not the complete microbe. The HiB vaccine, Hepatitis B and the Hepatitis A vaccines are subunit vaccines.
Toxoid Vaccines: These vaccines comprise of toxin secreting bacteria. The immune system receives harmless toxoid through this vaccine, making it easier to tackle the natural toxin. Examples of toxoid vaccines are the diphtheria and tetanus vaccines.
Conjugate Vaccines: To tackle bacteria having an outer coating of sugar molecules called polysaccharides, a conjugate vaccine is prepared. The most harmful bacteria contain such coatings. The vaccine contains toxins/antigens from a microbe that enables the immune system to recognize the polysaccharide coating.
How Vaccines Work
An individual can become immune to a disease in two ways – by getting the disease or by getting vaccinated for the disease. A vaccine is made with weakened or killed version of the antigen against which immunization is sought. When this antigen is injected into the individual’s body, it triggers a response in the immune system which develops antibodies to tackle this particular antigen. The next time the same antigen attacks the individual, the immune system will be immunized to counter the antigen and keep the disease at bay.
However, in order for the immunity to develop through a vaccine, it takes a long time. Usually, this is done through periodic administration of the vaccine over a particular span of time. The antibodies keep flowing through the blood in the body. Thus, vaccines ensure that the child remains free from diseases without the child ever contracting them in the first place.