The different categories of vaccines

1. A vaccine isa biological preparationthatimprovesimmunitytoaparticulardx.A vaccine typically
containsan agentthat resemblesadx cosingmicroorganism& is oftenmade 4rm weakenedorkilled
4rm of the microbe,itstoxinorone of itssurface proteins.The agentstimulatesthe body'simmune
systemtorecogize the agentas foreign,destroyit&rememberitsodt the immune systemcanmore
easilyrecognize &destroyanyof these microorganismsthatitlaterencounters. There are several
differenttypesof vaccines.Eachtype isdesignedtoteach the immune systemhow tofightoff certain
kindsof germs — and the seriousdiseasestheycause.Thereare 4 maintypesof vaccines:Live-
attenuatedvaccines,Inactivatedvaccines,Subunit,recombinant,polysaccharide,andconjugate vaccines
& Toxoidvaccines
Live-attenuatedvaccines
Live vaccinesuse a weakened(orattenuated)formof the germthat causesa disease.
Because these vaccinesare sosimilartothe natural infection they prevent,theycreate astrongand
long-lastingimmunethattheyhelp response.Just1or 2 dosesof most live vaccinescangive youa
lifetimeprotectionagainstagermand the disease itcauses.
But live vaccinesalsohave some limitations.Forexample:
Because theycontaina small amountof the weakenedlive virus,somepeople shouldtalktotheirhealth
care providerbefore receivingthem, suchaspeople withweakenedimmunesystems,long-termhealth
problems,orpeople who’ve hadanorgantransplant.
Theyneedtobe keptcool,sotheydon’ttravel well.Thatmeanstheycan’tbe usedincountrieswith
limitedaccesstorefrigerators.
Live vaccinesare usedto protectagainst:Measles, mumps,rubella(MMRcombined
vaccine)Rotavirus,Smallpox,Chickenpox,Yellowfever
Inactivatedvaccines
Inactivatedvaccinesuse the killedversionof the germthatcausesa disease.
Inactivatedvaccinesusuallydon’tprovideimmunity(protection) that’sasstrongaslive vaccines.Soyou
may needseveral dosesovertime (boostershots) inordertogetongoingimmunityagainstdiseases.
Inactivatedvaccinesare usedtoprotectagainst:HepatitisA,Flu(shotonly),Polio(shotonly),Rabies
Subunit, recombinant, polysaccharide, andconjugate vaccines
Subunit,recombinant,polysaccharide,andconjugate vaccinesuse specificpiecesof the germ — like its
protein,sugar,orcapsid (acasing aroundthe germ).
Because these vaccinesuse onlyspecificpiecesof the germ, theygive averystrongimmune response
that’stargetedto keyparts of the germ.Theycan alsobe usedon almosteveryone whoneedsthem,
includingpeople withweakenedimmunesystemsandlong-termhealthproblems.
One limitationof these vaccines isthatyoumay needboostershotstogetongoingprotectionagainst
diseases.
These vaccinesare usedto protectagainst:Hib(Haemophilusinfluenzaetype b) disease,HepatitisB,HPV
(Humanpapillomavirus),Whoopingcough (partof the DTaP combinedvaccine),Pneumococcal
disease,Meningococcal disease,Shingles
Toxoid vaccines
Toxoidvaccinesuse atoxin(harmful product) made bythe germthat causesa disease.Theycreate
immunitytothe parts of the germ that cause a disease insteadof the germitself.Thatmeansthe
immune response istargetedtothe toxininsteadof the whole germ.
Like some othertypesof vaccines,youmayneedboostershotstoget ongoingprotectionagainst
diseases.
Toxoidvaccinesare usedtoprotect against:Diphtheria,Tetanus
How dovaccineswork?

2. Vaccinesworkbystimulatingthe immunesystemtoproduce immunemoleculessuchasantibodies
(substancesproducedbythe bodytofightdisease).If youare vaccinatedandcome intocontact with
the disease itself,the antibodiesproducedfollowingvaccinationwill fightthe germsthatcancause the
disease avaccine wasgiventoprevent.
Vaccinationpromptsthe immune systemtoproduce itsownantibodies,asthoughthe bodyhas been
infectedwithadisease,butwithoutcausingsickness.Thisiscalled"active immunity".If avaccinated
personcomesintocontact withthe germ-causingdisease itself,the immune systemwillrecognise itand
immediatelyproduce the antibodiesneeded tofightit.
On administration,some vaccinesmaypromptthe immune systemtoproduce Tand B lymphocytes.
Subsequentlymemory Tand B lymphocytesare storedinthe body.If a germthat the vaccine was given
againstentersthe bodyof an immunizedperson,the memory TandB lymphocytesare releasedtofight
and eliminatethe germfromthe body,withoutthe persongettingsick.
Vaccine Preventable Diseases
Cholerais an acute intestinal infectioncausedbyingestionof foodorwatercontaminatedwiththe
bacteriumVibriocholera.
Dengue isa mosquito-borne flavivirusfoundintropical andsub-tropical regionsof the world,mostlyin
urban andsemi-urbansettings.Day-bitingAedesmosquitosspreaddisease.
Diphtheriais an infectiousdiseasecausedbythe bacteriumCorynebacteriumdiphtheria,which
primarilyinfectsthe throatandupperairways,andproducesatoxinaffectingotherorgans.
HepatitisA isa viral liverdisease thatcancause mildto severe illness.
HepatitisB isa viral infectionthatattacksthe liverandcan cause bothacute and chronicdisease.Itisa
majorglobal healthproblem,andthe mostserioustype of viral hepatitis.
HepatitisE isa viral liverinfectionwhichisusuallyself-limiting,butmaydevelopintofulminanthepatitis
(acute liverfailure).
Haemophilusinfluenzatype b (Hib) isa bacteriaresponsible forsevere pneumonia,meningitisand
otherinvasive diseasesalmostexclusivelyinchildrenagedlessthan5 years.
Human papillomavirus(HPV) causescervical cancer,whichisthe fourthmostcommon cancerin
women.
Influenzaisa contagious,acute respiratoryillnesscausedbyinfluenzaviruses,usuallyinfluenzaA or B
subtypes.Influenzacancause mildto severe illness,anditmaypredispose toexacerbationsof
underlyingdiseaseordevelopmentof secondarybacterial infections.
Japanese encephalitis(JE) isthe maincause of viral encephalitisinmanycountriesof Asia.The JEvirus
isa flavivirusrelatedtodengue,yellowfeverandWestNile viruses.The virusexistsinatransmission
cycle betweenmosquitoes,pigsand/orwaterbirds.Humansgetinfectedwhenbittenbyaninfected
mosquito.
Measlesisa highlycontagiousviral disease.Itremainsanimportantcause of deathamongyoung
childrenglobally,despitethe availabilityof asafe andeffectivevaccine.
Meningococcal meningitis,causedbyNeisseriameningitidis(meningococcus) isaleadingcause of
bacterial meningitisandsepticaemia.Endemicdiseaseoccursworldwide,withoutbreaksmost
frequentlyoccurringinthe “MeningitisBelt”of sub-SaharanAfrica
Mumps isan infectioncausedbyavirusand spreadhuman-to-humanviadirectcontactor by airborne
droplets.Itissometimescalledinfectiousparotitis,anditprimarilyaffectsthe salivaryglands.
Pertussisisa highlycontagiousdisease of the respiratorytractcausedby Bordetellapertussis,abacteria
that livesinthe mouth,nose,andthroat.Many childrenwhocontractpertussishave coughingspells
that lastfour to eightweeks.
Pneumococcal diseases,causedbyStreptococcuspneumoniabacterium.The bacteriumisthe cause of
a numberof common diseases,rangingfromseriousdiseasessuchasmeningitis, septicaemiaand
pneumoniatomilderbutcommonerinfectionssuchassinusitisandotitismedia.

3. Polio(poliomyelitis)isahighlyinfectiousdisease causedbyavirus.Itinvadesthe nervoussystemand
can cause irreversibleparalysisinamatterof hours.Polioisspreadthroughperson-to-personcontact.
Rabies isa zoonoticviral disease whichinfectsdomesticandwildanimals.Itistransmittedtoother
animalsandhumansthroughclose contact withsalivafrominfectedanimals(i.e.bites,scratches,licks
on brokenskinandmucousmembranes).Once symptomsof the disease develop,rabiesisfatal toboth
animalsandhumans.
Rotaviruses are the mostcommoncause of severe diarrhoealdisease inyoungchildrenthroughoutthe
world.AccordingtoWHO 2008 estimates,about450 000 childrenaged<5 yearsdie each yearfrom
vaccine-preventablerotavirusinfections;the vastmajorityof these childrenlive inlow-income
countries.
Rubellais transmittedinairborne dropletswheninfectedpeoplesneeze orcough,rubellaisanacute,
usuallymildviral disease traditionallyaffectingsusceptiblechildrenandyoungadultsworldwide.
Rubellainfectionjustbefore conceptionandinearlypregnancymayresultinmiscarriage,foetal death
or congenital defectsknownascongenital rubellasyndrome (CRS).
Tetanus isa non-communicabledisease contractedthroughexposuretothe sporesof the bacterium,
Clostridiumtetani,thatexistsworldwideinsoil andinanimal intestinal tracts,andassuch can
contaminate manysurfaces andsubstances.Tetanusoccurringduringpregnancyorwithin6weeksof
the endof pregnancyiscalled“maternal tetanus”,while tetanusoccurringwithinthe first28days of life
iscalled“neonatal tetanus”.
Tick-borne encephalitis isanimportantcause of viral infectionsof the central nervoussystemin
eastern,central andnorthernEuropeancountries,andinnorthernChina,Mongolia,andthe Russian
Federation.
Tuberculosis(TB) iscausedby a bacterium, Mycobacteriumtuberculosis(Mtb).Itisacurable and
preventabledisease thatmostoftenaffectsthe lungs.TBistransmittedfrompersontoperson,by
people withpulmonary(lung) TBwhorelease Mtbintothe air throughcoughing,sneezingorspitting.
Typhoid feverisan infectioncausedbythe Salmonellatyphi bacterium,usuallythroughingestionof
contaminatedfoodorwater.The acute illnessischaracterizedbyprolongedfever,headache,nausea,
lossof appetite,andconstipationorsometimesdiarrhoea
Varicella,alsocommonlyreferredtoas“chickenpox”,isanacute and highlycontagiousdisease.Itis
causedby primaryinfectionwiththe varicella-zostervirus(VZV).Varicellaoccursworldwide andinthe
absence of a vaccinationprogramme,affectsnearlyeverypersonbymid-adulthood.
YellowFever(YF) isa mosquito-borne viral diseaseof humansandotherprimates,andiscurrently
endemicinover43 countriesinthe tropical regionsof AfricaandThe Americas.Infectionwiththe YF
viruscan be asymptomaticor cause a wide spectrumof disease,frommildsymptomstosevere illness
withbleeding,jaundice and,ultimately,death.