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IMMUNIZATION

Immunization – The creation of immunity usually against a particular disease; especially : treatment (as by vaccination/ immunoglobulin) for the purpose of making a person immune to a particular pathogen

Widespread vaccination led to small pox eradication Widespread immunity due to vaccination is largely responsible for the worldwide eradication of a very deadly and lethal virus called smallpox virus and the restriction of diseases such as polio, measles, and tetanus from much of the world.

1798 vaccine developed All viruses within the Orthopoxvirus genus are so closely related that infection with one induces an immunity to all other members In 1796, an English doctor Edward Jenner observed, milkmaids infected with cowpox (a very mild disease) never seemed to get smallpox. He inoculated, an 8 year old boy, with cow pox virus and a month later with live smallpox virus.The boy was completely protected and did not show any symptoms. This was the first ever vaccine, infact the word vaccine is derived from Latin word for cow, vaccinus

1967, WHO campaign In 1967, WHO launched an intensified plan to eradicate smallpox Worlds last indiginous patient of small pox was a hospital cook in Merka, somalia, in October 26, Finally in 1979 WHO declared small pox eradicated from the world

Types of immunization Active immunization – Active immunization is the induction of immunity after exposure to an antigen Natural – Exposure to microbe Artificial – use of vaccine. Passive immunization – Use of preformed antibodies from another host natural – Mother to fetus Artificial – Use of immunoglobulins

Vaccination – Artificial induction of immunity by using vaccines Vaccine – A preparation of a weakened or killed pathogen, such as a bacterium or virus, or of a part of the pathogen's structure that upon administration stimulates antibody production or cellular immunity against the pathogen but is incapable of causing severe infection itself

Types of vaccines Three types of vaccines – Live attenuated vaccine – Killed vaccine – Subunit vaccine

Live attenuated vaccine Live attenuated vaccine ( لقاح حي موهن ) – A live attenuated vaccine contains live microbe whose pathogenicity (disease causing ability) has been attenuated(reduced) but it still retains its antigenicity to induce immunity

Advantages – Live attenuated microbes induce longer and greater immunity as they multiply in the body – Excretion of microbe by the vaccinated individual transmits it to other nonimmune contacts so that they also get vaccinated

Disadvantages An important problem is that the live microbe may change back to normal microbe causing disease; only polio virus has this problem Maintenance of cold storage Should not be given to immunocompromised and pregnant woman

Killed vaccine Killed vaccine or inactivated vaccine – Vaccines of this type are created by inactivating a pathogen, typically using heat or chemicals such as formalin. This destroys the pathogen’s ability to multiply, but keeps it antigenicity“intact” so that the immune system can still recognize it. Toxoid vaccine is inactivated exotoxins of bacteria whose toxicity is destroyed but antigenicity is retained e.g diphtheria and tetanus toxoid

Advantages & disadvantages Advantages – Cannot revert back to normal – No cold chain Disadvantages – Immunity is shorter and weaker – No immunity of the contactss

Subunit vaccine Subunit vaccines use only part of a microbe to provoke an immune response. – isolating a specific protein from a pathogen Recombinant vaccine – A gene from the pathogen, coding for a protein antigen is inserted into genome of a producer cell which expresses it. – Hepatitis B vaccine contains one of the viral envelope proteins, hepatitis B surface antigen (HBsAg). It is produced by yeast cells, into which the genetic code for HBsAg has been inserted – The expressed protein is isolated and injected as vaccine

Conjugate vaccine Conjugate vaccines are made using a part from the pathogen and chemically attaching it to a carrier protein to create a more powerful immune response: – typically the “piece” of bacteria being presented would not generate a strong immune response on its own, while the carrier protein would. – e.g pneumococcal vaccine in children

Immunoglobulins Passive immunity Use of preformed antibodies developed in another host Immediate protection as compared to vaccines which take few days to stimulate antibody production Immunity is only short lived ( as long as the antibody remains in the body) e.g hepatitis B passive immunization with immunoglobulins, rabies passive immunization with immunoglobulins

Hepatitis B post exposure prophylaxis Hepatitis post exposure prophylaxis is an example of both active & passive immunization Immediately after exposure to an hepatitis B positive case prophylaxis is begin in the form of one dose subunit vaccine and one dose HBIG(hepatitis B immunoglobulin) HBIG provides immediate protection (bind and remove any virus)and vaccine will stimulate a stronger antibody production after a few days

Rabies Postexposure prophylaxis Rabies is a very fatal central nervous sytem infection caused by rabies virus It is 100% vaccine preventable The virus has a long incubation period of 1-3 months PEP is administered after exposure to a rabid animal before virus could enter CNS PEP includes both active and passive immunization

Rabies Postexposure prophylaxis Rabies immune globulin (RIG)(passive immunization) – Preformed antibodies in the form of RIG is administered – If possible, the entire dose of RIG (20 IU/kg) should be infused at the site of the bite; otherwise, administered IM at a distant site Rabies vaccine(active immunization) – The five doses of killed rabies vaccine should be given on days 0, 3, 7, 14, and 28 – 1ml IM dose in deltoid region

Tetanus postexposure prophylaxis Tetanus is a bacterial infection after clostridium tetani spores in soil enter open wounds Patient goes into violent spasms(muscle contractions) It is common in emergencies to give both vaccine and immunoglobulin after road side injuries to prevent tetanus(active-passive immunization)

WHO EPI programme The World Health Organization (WHO) initiated the Expanded Program on Immunization (EPI) in May 1974 with the objective to vaccinate children throughout the world. Vaccination coverage for tuberculosis, diphtheria, pertussis, tetanus, polio, measles, hepatitis B, Haemophilus influenzae type B and rubella Started at birth

List of vaccines