Vaccines are important in human health and disease, More understanding is needed to explore the implications and limitations of newer generation of vaccines.in clinical practice
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a. Live attenuated organisms which have been passed repeatedly in tissue culture or chick embryos so that they have lost their capacity to cause disease, but retained an ability to induce antibody response, such as polio (Sabin), measles, rubella, mumps, yellow fever, BCG, typhoid and plague.
b. Inactivated or killed organisms which have been killed by heat or chemicals but retain and ability to induce antibody response. They are generally safe but less efficacious than live vaccines and require multiple doses; e.g. polio (Salk), influenza, rabies and Japanese encephalitis.
c. Cellular fractions: usually polysaccharide fraction of the cell wall of a disease causing organism, such as pneumococcal pneumonia or meningococcal meningitis
d. Recombinant vaccines: produced by methods in which specific DNA sequences are inserted by molecular engineering techniques, e.g. DNA sequences spliced to vaccinia virus grown in cell culture to produces an effective influenza vaccine, and Hepatitis B vaccine by similar methods.
Toxoids or antisera: are modified toxins made non-toxic to stimulate formation of an antitoxin, such as those produced to protect against toxins of tetanus, diphtheria, botulism, gas gangrene, snake and scorpion venom.
Immune globulin: An antibody containing solution derived from human blood in the form of pooled plasma, used primarily for immunity for passive immunization such as for immuno-compromised persons e.g. smallpox response groups.
Antitoxin: is an antibody derived from serum of animals after stimulation with specific antigens and used to provide passive immunity in humans.
*Estimated future use
**Used in ~ 50% of global birth cohort
The Global Burden of Disease
Murray and Lopez, editors
Total - 12.8 million
Polysaccharide vaccines (vaccines made from complex sugars taken from the outer coats of the Men bacterium) are currently in use, but are not very effective at protecting young children, do not create long-lasting immunity, and do not confer a "herd effect". Because of these shortcomings, immunization with polysaccharide vaccines is usually undertaken only after the onset of an epidemic.
Acute diarrhoea is responsible for nearly 1.9 million deaths per year in children under age five. Rotavirus is responsible for as much as one fourth of these casualties, almost all of which occur in developing countries.
H. pylori is among commonest bacterial infectionsin humans, and may be be transmitted by water and oral fecal spread.
Genomics may helpunderstanding the pathogenesis of H. pylori infectionand development of new therapies, includingH. pylori–specific antimicrobial agents and vaccines
Enormousprogress in studying the virulence factors ofH. pylori and their variation, but not yetused in clinical practice
Px and Rx vaccination have been successfulin animal models, but the translation to human vaccine remainsdifficult
These developments willbe needed to prevent and treat this infection in areasof the world where there is a high prevalence of chronic infection
From Scientific American, July 1995
They can bring untold damage to immunization programs and cause diseases and deaths