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Vaccination contributed in reduction of morbidity and mortality among children worldwide. Now a days vaccines are used for routine immunization during first 18 months of life . Some of them are diphtheria tetanus poliovirus vaccine measles mumps rubella hepatitis and so on. Some vaccines are for adults such as Hep b vaccines , influenza vaccines. Appropriate use of vaccines has resulted in some of the major disease like smallpox.
They are 2 types of vaccines
LIVE ATTENUATED VACCINES :In these types of vaccines there will be live virus particles with low virulence factor. These type of vaccines produce long lasting immunity with single dose. These type of vaccines help in replication of immune cells and offer life long protection with one dose. These type of vaccines should not be administered to immunocomprimsed people
INACTIVATED VACCINES: These type of vaccines are produced by destroying microorganism completely.These vaccines require multiple dosage .Live vaccines are not always used so killed vaccines are used for immunization.
Use Of vaccines
1) Routine use of vaccines for infants and children:
Such as DTP, polio, measles, mumps, rubella, Hemophilus influenza type B, and HBV vaccines. Four doses of DTP and three doses of OPV is the primary series.
2) Adults: all the adults should be immunized to diphtheria and tetanus. Routine immunization to polio is not recommended for adults unless they are at particular risk of exposure, as with travel to endemic areas.
3) Use of vaccines in special circumstances:
Ø Pregnancy: because of the theoretical risk to the fetus and the real risk of litigation to the practitioner, routine immunization to women is avoided. Although live vaccines in general are withheld during pregnancy but killed vaccines can be administered to the pregnant women. (E.g., influenza.)
Ø Breast feeding: breast-fed infants can be immunized on a normal schedule. Breast feeding does not adversely affect the immune response. Breast feeding women may also be vaccinated without any problem.
Ø In people with HIV and immunocompromised states should be immunized as normal person but live/attenuated vaccines sholu not be given.
Ø Occupational exposure: immunization should be recommended for the occupational group specially for hepatitisB.
Ø Postexposure immunization: for certain infections , active or passive immunization soon after exposure prevents or attenuates disease expression.
Immunization and immunization Principles.
Immunization: A process which renders to organism immunity to a specific disease by exposing the organism to an antigen to promote the production of antibodies to a particular antigen.
1) Passive immunization: This occurs naturally by the transfer of mothers antibodies to fetus.
This can also be acquired artificially by inducing animals antibody to humans but for passive immunity the body does not devlop memory .
2) Active immunization: Can be attained by use of live atteneuated infectious agents.for eg measles virus
Use of inactivated agents also attain active immunity eg Pertussis vaccines.
3)Routes of administration:This is used for determining the nature of immune responses to the vaccines
These can be administered in many ways such as intranasal intradermal subcutaneous and IM , IV.
• Immunization is recommended based on age-dependent responses.
• For e.g., infant has immature immunity and maternal antibodies, while elderly people vaccine response may be diminished because of natural waning of the immune system.
5) Adjuvant Potentiation:Immune response is potentiated by adding adjuvants as aluminium and are used in inactivated toxins .
6) Immune response :
Primary response :This is charecterised by early appearance of IgM antibodies.After wards CD4 lymphocytes which shifts IgM to IgG having high affinity and more specific antibody.
Secondary response: Elicted by humoral and cell mediated response in second exposure to antigen.
Hypersensitive reaction: The stimulation of the immune system by vaccination may elicit unanticipated
responses, especially hypersensitivity reactions.
7)Mucosal immunity: Some pathogens are confined to and replicate only at mucosal surfaces (e.g., Vibrio cholerae), while others are able to penetrate the mucosa and replicate (e.g., poliovirus, rubella virus, andinfluenza virus). At the mucosal site, these organisms induce secretary IgA. The induction of secretory IgA by vaccines may be an efficientway to block the essential first steps in pathogenesis, whether the organisms restricted to mucosal surfaces or invades the host across mucosal surfaces.
8) Herd immunity:
• Vaccination of individual give direct protection from infection of individual which decrease the %susceptible persons within a population. Therefore if prevalence of immunization in increased in a population, infection will not circulate and the remaining small % of unvaccinated person is indirectly protected.
9) Target populations and timing of immunization:
• Different age group differ in disease attack rate
• Depending on how people often exposed to disease immunization should be given as early in life as feasible.
• Vaccination programme is effective if applied to community not to an individual.