Immunoprophylaxis
Vaccines are intended to prevent diseases and their impact is to activate the immune system and results in protective immunity and may confer state of what is so called herd immunity in which when the majority of people is immune so the chance of microorganisms infecting the non immunized individuals is small.
Immunization could be natural or artificial. In natural Immunization the individual does not seek service but it takes place naturally. Natural vaccination is either passive or active. The example of passive natural Immunization is passage of antibodies from mother to fetus in utero through the placenta. An example of active natural vaccination is if someone get bitten by female mosquito which inoculate sporozoites and then the body makes immune responses to these parasites, so it starts naturally and ends in an active way by producing antibodies and Cellular immunity against the parasite.
Artificial Immunization means that the individual seeks Immunization at health centers . Artificial vaccination is subdivided into either passive or active Immunization. In artificial passive Immunization an individual gets ready made antibodies raised in animals for example Immunization against diphtheria and hepatitis A.
Artificial active vaccination means that the individual gets purified macromolecules e.g. Toxoids, recombinant antigens or vector and also can be achieved by injection of whole pathogens either inactivated or attenuated pathogens. Attenuation is achieved by growing microorganisms in unfavorable media for example mycobacterium Boris in urea as in case of BCG vaccine that protects against mycobacterium tuberculosis . Other example of attenuated vaccine is Sabin polivaccine which consists of three attenuated policies. Inactivated or killed vaccine has the capacity only to stimulate antibody formation. In contrast attenuated vaccine has the capacity to induce both cellular and antibody immune responses. Recently DNA and RNA Vaccines were introduced e.g. AstraZeneca and Pfizer Vaccines against covid19.
Adjuvant is a substance that increases the effectiveness of the vaccine and enhances the immune responses to the vaccine.