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Importance of vaccination for viral diseases

Antivirals. Anti HIVReverse transcriptase inhibitorsProtease inhibitorsFusion inhibitorsAnti HBV3TC. Antivirals. Anti HCVInterferon/ribavirinAnti InfluenzaFusion inhibitors: oseltamivir (Tamiflu)Cleavage inhibitors: amantadine, rimantadine Ribavarin general antiviral mixed success, tox

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Importance of vaccination for viral diseases

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    1. Importance of vaccination for viral diseases Unlike bacterial infections where antibiotics are in general effective (although there is an increasing problem of resistance), there are few effective and safe antivirals, emphasising the need for effective vaccines.

    2. Antivirals Anti HIV Reverse transcriptase inhibitors Protease inhibitors Fusion inhibitors Anti HBV 3TC

    3. Antivirals Anti HCV Interferon/ribavirin Anti Influenza Fusion inhibitors: oseltamivir (Tamiflu) Cleavage inhibitors: amantadine, rimantadine Ribavarin general antiviral mixed success, toxicity problems

    4. Primary/secondary immune response The aim of vaccination is to mimic the effect of the primary infection in the absence of disease and prime the appropriate immune response (both antibody IgG/A and T-cell). When the virus is encountered there is a more rapid and larger immune response which limits virus replication and spread and clears the virus prior to the initiation of disease.

    5. Purpose of vaccination Classically the aim of vaccination is to prevent disease not necessarily infection. This is satisfactory for an acute infection such as measles. Not necessarily adequate for viruses, such as HIV or HSV, which establish latent/persistent infections probably in the absence of replication.

    6. Herd immunity If a certain % of the population is vaccinated (typically 90+%), unvaccinated individuals will also be protected as the virus will not have a large enough reservoir to spread rapidly through the population. This is partly the aim of large school/community based vaccination programmes. Studies with influenza vaccination have demonstrated that the most effective way to protect elderly patients in residential care is to vaccinate the health care workers and thus prevent them infecting their patients. Partly because the ability to mount an immune response to vaccination (and infection) falls with age.

    7. Live versus inactivated vaccines (1) Live attenuated viruses replicate to a limited extent Mimic natural infection Only 1 dose usually required Lower dose Antibody response: both serum IgG and if appropriate a mucosal IgA More likely to prevent initial infection T-cell response Potential to revert to pathogenic virus Less stable

    8. Live versus inactivated vaccines (2) Killed vaccines do not replicate High dose with booster injections required Only serum IgG response Problem of incomplete inactivation Generally stable as only protein

    9. Live attenuated vaccines Polio Sabin strains Vaccinia Measles Mumps Rubella Varicella-zoster

    10. Inactivated vaccines Polio Salk strains Hepatitis A (Hepatitis B) Rabies Yellow fever Influenza

    11. MMR Vaccination Indications All children in the second year of life Booster at school entry Important for long lasting immunty Administration 1 dose of live attenuated MMR Protection Evidence that immunity wanes Surveillance important

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