types of vaccines live – live pathogens dead – killed pathogens attenuated – weakened...

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1 Types of Vaccines Live – live pathogens Dead – killed pathogens Attenuated – weakened pathogens Toxoids – toxins (made harmless) DNA Edible vaccines Vaccinati on

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Vaccination. Types of Vaccines Live – live pathogens Dead – killed pathogens Attenuated – weakened pathogens Toxoids – toxins (made harmless) DNA Edible vaccines. Vaccination. Inducing a specific immune response to a pathogen artificially – Antigen injected or taken orally – not caught. - PowerPoint PPT Presentation

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Page 1: Types of Vaccines Live – live pathogens Dead – killed pathogens Attenuated – weakened pathogens

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Types of Vaccines

Live – live pathogens

Dead – killed pathogens

Attenuated – weakened pathogens

Toxoids – toxins (made harmless)

DNA

Edible vaccines

Vaccination

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Living attenuated (“weak”) microbes Administration of microbes that have lost the ability, either naturally (through mutation) or by treatment in the laboratory, to produce the dangerous, clinical disease – e.g the cowpox virus, measles, mumps and rubella (MMR vaccine) and polio (oral) vaccine virus.

Vaccination - consists of infecting a person with a living attenuated microbe which then produces a limited infection. The immune system of normal healthy people quickly kills and eliminates them from the body. The infection elicits a primary immune response that results in the production of memory cells. The host is protected from infection (disease) by the virulent, disease-producing form of the injected microbe used in the vaccine.

Live vaccines produce the best immunisation because they closely imitate the real thing. Immunity lasts for life.

Dead Microbes Cultures of the pathogenic microbial strains killed in such a way that they retain their ability to stimulate the body to produce an immunological response to the live form – e.g. anthrax and rabies vaccine; polio (injected form); influenza

Immunity lasts several years.

VaccinationInducing a specific immune response to a pathogen artificially – Antigen injected or taken orally – not caught

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Vaccination using components of pathogensVaccines consisting of substances isolated from the virulent strains, such as polysaccharide material or proteins components. No whole organisms, living or dead are present in these vaccines – e.g. polysaccharide from pathogenic Pneumococci; hepatitis A and B; Haemophilus influenzae

Vaccinations by eating ( “edible” vaccines) Experiments are underway to deliver vaccines through common foods like potatoes and bananas. Genes that make an antigen effective against a microbe are cloned into a common food. The food is eaten by the "patient" and the cloned-antigen stimulates the immune system.

DNA Vaccines Vaccines consisting of DNA fragments that can be transformed into host tissue.

Once in the host tissue, the DNA is transcribed and translated and the protein produced is seen by the specific immune system as foreign material and an immune response is induced.

Toxoid vaccinesMade by treating toxins (or poisons) produced by pathogens with heat or chemicals (e.g. formalin) – destroys ability to cause illness - e.g. diphtheria, tetanus, botulinum.

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Artificial active immunity (Vaccination)Ag injected/taken orally (not caught)

VaccineAdministration of Ag or attenuated/weakened/dead/similar pathogento activate Immune system – causes immune responseEngulfed by phagocytesAg’s presented on cell surface membraneSelection/production of active Th cells (lymphocytes)T cells divide by mitosis to form a cloneSome form memory cellsSecrete cytokines (lymphokines)Activate B cellsB cells divide by mitosis to form a cloneMajority mature into antibody secreting plasma (effector) cellsSome form memory cells – remain in bodyAllows a more rapid and stronger secondary responseNo symptoms of disease on vaccination

Use of vaccines in eradication programmesHerd vaccination (vaccinate most/all of people) – stops infection spreading within populationRing vaccination – vaccinate all people around victim – contains spread within ring – stops transmissionTrace and isolate contacts; travel restrictions; make disease notifiable

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The safety of medical procedures and agents always carry a degree of risk, The live vaccines present the highest risk because it is always possible that a mutation may occur that reverts the avirulent strain to virulence or that a particular individual will be susceptible to the avirulent strain; i.e., that it will be "virulent" only for that individual. This has happened in the case of smallpox where an occasional person, usually a child, develops a severe, often fatal, disease caused by the smallpox vaccine.

Killed vaccines have had safety problems when the lethal treatment failed to kill 100% of the microbes. The problem is that if you over treat the microbe to be certain that all the organisms are dead you can destroy the immunising components and make the vaccine ineffective. So the killing treatments must balance. .

Vaccination – not effective in eradication of some diseases - factors

Difficult to diagnose diseaseNot enough population vaccinated – need herd immunityPoor response to vaccineMigrants bringing disease into a communityLength of time vaccine remains effective (boosters)Mutation of pathogenSeverity of disease – affects decision to get vaccinatedConcerns as to side-effects – people reluctant to be vaccinated

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Successful Vaccine – e.e. Smallpox

Stable pathogen – does not mutate – one type of AgLive vaccive – more effective (c. 100%)Easy to produce; cheap; high availabilityEasy storage; freeze-dried; heat stableInfected people easy to identify and cooperativeEasy to administer; reusable needle; no booster needed (only one inoculation)No other reservoir of infection – only human hostFundsVolunteers /spotters used to find new cases

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Modern vaccines are about as safe as anything in this dangerous world. Everyone who drives or is driven on the highways is in far more danger of harm than they are being vaccinated.

The UK is one of the safest countries in the world when it comes to communicable diseases, but we probably are not the safest. Diseases are always present and they do not recognise borders.

We are so intimately connected with the rest of the world today that diseases can appear from anywhere. The strawberries or lettuce you just purchased at the supermarket yesterday may have come from a country with far less sanitation than we practice, or the person you sit by on the bus may be a recent immigrant or traveller coming from another country that is carrying a disease the UK is "free" of. In these cases your only real protection is vaccination. Think about it!

Also it is difficult to detect the one live organism present in a 1,000 liters of treated material, yet one live organism is sufficient to produce a lethal infection.

The use of chemical components of pathogens also carries some risks. Some people will react violently to these substances, usually in an allergic reaction, and they can be seriously harmed or even killed as a result. The DPT vaccine combination has caused such reactions

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Influenza (flu) virus –

Capable of mutationChanges antigenic structure – change in glycoprotein structure -antigenic shift

Vaccine against one strain not effective against another strain of the influenza virus

Need to develop new vaccines each year for prophylaxis

Surface proteins (neuraminidase + haemagglutinin) act as antigens

Antigens change structure regularly – forming new strains of the virus

Memory cells from infection from previous strain do not recognize new strains (antigens)

WHO + CDC monitor emergence of new strains and collect samples

New vaccines developed (in chicken eggs) against the new strains– one chosen that is most effective against the recently circulating strain

Authorities implement a programme of vaccination

Treatment of Influenza – Challenges – use of science to inform decision making

Bacteria – mutate - antibiotic resistance (e.g. MRSA); ineffective vaccines

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Malaria – vaccinesLoss of immunity on leaving a malarial area

No repeat infections – no further exposure to Ag – no boosterLose immunological memory – limited life for memory cells – reduced

number of memory cellsNo secondary response

No effective malarial vaccine

Different strains / species of Plasmodium; different antigens – due to mutation / variation

More than one stage of life cycle (within human); different stages have different Ag’s

Need a different vaccine for each strain / stage

Parasite concealed in cells – RBCs and hepatocytes

Parasite only exposed in circulation for short time

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Sources of Medicines

Many drugs obtained from or made from natural substances found in plants, animals, microorganisms (bacteria) , and fungi – e.g.

Only a limited number of organisms investigated so far – numerous others exist – to be investigated

Need to protect above sources of drugs by protecting the species and maintaining biodiversity

Species may die and become extinct before being studied

Organisms already studied could provide additional substances for use as drugs due to development of powerful new techniques for identifying, purifying, and testing compounds. Use of bacteria in genetic engineering

Streptomycin – antibiotic in TB – from bacteriaPenicillin – antibacterial – from Penicillium (fungus)Quinine – antimalarial – Cinchona treeInsulin (hormone) – antidiabetic – pigs; cowsEnzymes – pancreatic – for CF – from animalsAspirin – analgesic / antiinflammatory - bark of willow treeTamoxifen – anticancer – Pacific Yew treeCinnamon – antidiabeticStar anise – Tamiflu – antiviral – from shikimic acid

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Passive immunization is provided in the following circumstances:When people cannot synthesize antibody.When people have been exposed to a disease that they are not immune to or that is likely to cause complicationsWhen people have a disease and the effects of the toxin must be ameliorated.

Boyulinum antitoxinDiphtheria antitoxinImmune globulin (poled human antibodies) – prophylaxis; immunodeficiency disordersRabied immune globulinTetanus immune globulinAntivenom antibodies (spiders; snakes; scorpions; ticks; caterpillars; jellyfish

PreparationInject Ag (toxin) into animal – produces antibodies – antibodies harvested – must conform to WHO standards prior to use