immunization

Immunization
Specificdefences:Micro organism-breach local defense systemshost recognize, destroy and eliminate antigenicmaterial foreign to its ownSpecific defenses are1.Active immunity –humoral, cellular , combined immunity2.Passive immunity – normal humanIg,specifichumanIg, animalantitoxin orantisera
Active immunity- Immunity developed as a result of infection or by specific immunization and is usually associated with the presence ofAbor cells having specific action on micro organism or its toxin. - Immunity produced is specific for particular diseases
Active immunity may be acquired by following :-clinical infection-sub clinical or in apparent infection-immunization with an antigen
THE IMMUNE RESPONSE
Primary response:-Agfirst time administerIgMAb-----IgGAb-Nature and extend of primary response to anAg is determined by factors like-Dose of Ag, nature of Ag, route ofadministration, nutritional status of the host etc.
Following primary response RES is educated . There s production of memory cells by both B & T lymphocytesThese cells are responsible for immunological memory which become established after immunizationIn fact purpose of immunization is to develop immunological memory.
B. Secondary (booster) response:-secondary response involve production of bothIgM&IgGantibodyResponse to booster dose differs in a no. of ways from primary responseProduction ofAbmore rapidAbresponse maintained at higher level for a long period of timeAbtends to have a greater capacity to bind to Ag
Humoralimmunity
It comes from B cells (bone marrow derived lymphocytes) which proliferate and manufacture specificAbafter Ag presentation by macro phagesImmunoglobulin's are divided into 5 classes –IgG, M,A,D &E .they circulate in body and neutralizes the microbes/toxinsAbare specific- they react with same Ag when provided
Cellular immunity
Some micro organism likeM.Leprae, M.TB escapehumoralimmunity and can multiply in macrophages . However these macrophages can be stimulated by T-lymphocytes.The activated macrophages perform a much more efficientphagocyticfunction than non- activated macrophagesT cells do not secreteAb, but they are responsible for recognition of Ag
Combination of both
In some cases they jointly helps in immunityVaccine to be effective mustellicitboth cell mediated andhumoralresponses
Active immunity takes time to develop . It is superior to passive immunity becauseduration of protection is long lastingWith few exceptions severe reactions are rareProtective efficiency is better than passiveActive is less expensive
Passive immunity
Abproduced in one body ( human / animal ) are transferred to another to induce protection against diseaseThat is, they are ready madeAbPassive immunity may be induced byIgor anti serum administrationAbthrough placenta , human milk (IgA)
Passive immunity differ from active immunity byImmunity is rapidly establishedImmunity produced is only temporary ( days to months ), till whenAbis eliminated from the bodyThere is no education of RES
Herd immunity
It is the level of resistance of a community or a group of people to a particular diseaseEg: polio vaccine-------,chickgunyainAlappuzhaElements contributing to herd immunityOccurrence of clinical or sub-clinical infection in herdImmunisationof the herdHerd structure
If herd immunity high enough , occurrence of epidemic is highly unlikelyHerd immunity is maintained byimmunisationEg: polio , diphtheriaWith no vaccine for small pox herd immunity is declined
Immunisingagents
Vaccines- substances-designed to produce specific protection against a given diseaseIt stimulate production of protectiveAbLive vaccine (attenuated )Prepared from liveorganisum. Doesn’t have the property ofphathogenicitybut retained immunogenicityShould not be administered to immune deficient people, pregnancyIf two live vaccine required – either given at two sites simultaneously or with an interval of at least three weeksShould be properly storedUsually require only one dose , exception of polioEg: polio , BCG , measles , rubella
(b) Inactivated / killed vaccineVirus is killed with heat or chemicals and infected into the body to stimulate active immunityThey are usually safe but less efficacious than live vaccinesUsually require more than two to three primary and even a booster dose to produce adequateAbresponseUsually administeredi/m or s/cOnly severe C/I is severe local or general reaction to previous doseEg:pertusis, IPV, typhoid
Toxoid:Exotoxinsproduced by certainorganisumaredetoxicatedand used to prepare vaccinesTheseAbproducedneutralisesthe toxin moiety produced during infection and not the organismHighly efficacious and safeEg: tetanus and diphtheria
Cellular fraction:Prepared from extracted cellular fractions like cell wall, capsule etcEfficacy and safety highEg:meningiococcal, pneumococcalCombination:Simplify administration, reduce cost,minimiseno. of contact of patient with health systemEg: DPT , MMR,Pentavalent
Polyvalent : prepared from two or more strains of same species .Eg: polioinfuenzaAutogenousvaccine : organism in vaccine is obtained from the same patientVaccine can be plain , adjuvant , freeze dried preparationAdjuvant is added to vaccine with an intent of potentiating the immune response.eg :aluminiumphosphate,aluminiumhydroxideFreeze dried vaccines ( BCG , Measles , YF) are more stable preparations than liquid vaccines
Immunoglobulin
Composed of five major classes and its sub units-IgG,M,D,A,EIgpreparations : two typesNormal humanIgSpecific humanIg– usually made from plasma of patients who have recently recovered from infectionLive vaccine should not be given normally for 12 weeks after giving normal humanIgand if already givenNHIgshould be differed for 2 weeksEg:HepA,HepB, Tetanus, Rabies
Antiseraand antitoxins
They are materials prepared in animals ( horses)Passive immunization is achievedEg: tetanus, snake bite, diphtheria
Cold chain
It is the system of storage – transportation of vaccines from themanufatureto the actual vaccination sitePolio is most sensitive to heat among vaccines requires storage at -20 degree C.Vaccine stored in freezer compartment are polio and measlesVaccine in cold part but never allow to freeze are ‘T’ series vaccine, DPT, TT,DT,BCG & diluents
Vaccine should be protected from sunlight and antisepticsIf refrigerated temperature is kept between 2 and 8 degree C vaccines (except polio) can be storedupto5 weeksReconstituted BCG and measles are kept +2 to +8 degree C for max, of 4 hours and JE vaccineupto2 hoursReturn the unused vaccine vial to PHC from site on the same day in cold chainDiscard vaccine that are unused more than 3 times
Cold storage equipment
(a)Walk-in cold room:Located at regional levelmeant to store up to 3 monthsServe 4 to 5 districts(b) Deep freezer:supplied to all districts (large) & PHC (small)Cabinet temperature is -15 to -25 degree CIn case of power failures they can maintain cabinet temperatureupto18 to 22 hoursAt PHC level deep freezer are used only for ice pack preparation and not for vaccine storage
( c)Ice lined refrigerator ( ILR):Kept at district ( large) and PHC (small)Cabinet temperature is maintained at +2 to +8At PHC, ILR are used to store vaccinesILR are lined with tubes or ice packs to maintain internal temperatureILR can keep vaccine safe with 8 hours of continuous electricity supplied in a 24 hour periodThey are top opening – can hold cold air inside better than front openingVaccine kept in basket along with diluentsKeep spaces with boxes
A dial thermometer is kept in ILR and temperature is recorded twice a dayIn case of electric supply failure or during defrosting vaccines transferred to cold boxesDO’S -keep away from direct sunlight and 10 cm away from wall ,keep voltagestabiliser,keep equipmentlevelled,keep space between vaccines for air circulation,open only when necessary, defrost periodically
DONT’S– Not to keepanyotherequipments drugs ,food, water inside itDiscard expired vaccine(d) Cold boxes:Supplied to all peripheral centersUsed mainly for transportation of vaccinesIce pack are placed at bottom and sidesVials of DPT , DT , TT & diluents should not be placed in direct contact with frozen ice packs
(e) Vaccine carrier:Used to carry small quantities of vaccine ( 16 to 20 vials)4 frozen ice pack are used for lining the sides(f) Day carrier :Used to carry small quantity (6 to 8 vials)2 frozen ice packs are to be usedUsed only for few hours(g) Ice packs:Only water is filleduptothe level markedIf leaking discarded-risk of cold chain failure is greatest at sub-centre level. Hence , vaccines are not stored there.
Vaccine vial monitor(VVM)Adverse events following immunization(AEFI)Vaccine reactionProgramme errorCoincidentalInjection reactionUnknown--precautions to be takenContra indications of vaccine
NIS- national immunization scheduleUIP – universal immunization programme–infancyEPI – expanded programme on immunization – till 5 yearsPulse polio immunizationCatch up- keep up- follow up