Types of Vaccines Live – live pathogens Dead – killed pathogens Attenuated – weakened pathogens

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

2. Vaccination Inducing a specific immune response to a pathogen artificially – Antigen injected or taken orally – not caught 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.

3. Vaccination using components of pathogens Vaccines 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 Toxoid vaccines Made 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. 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.

4. Artificial active immunity (Vaccination) Ag injected/taken orally (not caught) Vaccine Administration of Ag or attenuated/weakened/dead/similar pathogen to activate Immune system – causes immune response Engulfed by phagocytes Ag’s presented on cell surface membrane Selection/production of active Th cells (lymphocytes) T cells divide by mitosis to form a clone Some form memory cells Secrete cytokines (lymphokines) Activate B cells B cells divide by mitosis to form a clone Majority mature into antibody secreting plasma (effector) cells Some form memory cells – remain in body Allows a more rapid and stronger secondary response No symptoms of disease on vaccination Use of vaccines in eradication programmes Herd vaccination (vaccinate most/all of people) – stops infection spreading within population Ring vaccination – vaccinate all people around victim – contains spread within ring – stops transmission Trace and isolate contacts; travel restrictions; make disease notifiable

5. Vaccination – not effective in eradication of some diseases - factors Difficult to diagnose disease Not enough population vaccinated – need herd immunity Poor response to vaccine Migrants bringing disease into a community Length of time vaccine remains effective (boosters) Mutation of pathogen Severity of disease – affects decision to get vaccinated Concerns as to side-effects – people reluctant to be vaccinated 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. .

6. Successful Vaccine – e.e. Smallpox Stable pathogen – does not mutate – one type of Ag Live vaccive – more effective (c. 100%) Easy to produce; cheap; high availability Easy storage; freeze-dried; heat stable Infected people easy to identify and cooperative Easy to administer; reusable needle; no booster needed (only one inoculation) No other reservoir of infection – only human host Funds Volunteers /spotters used to find new cases

7. 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 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!

8. Treatment of Influenza – Challenges – use of science to inform decision making Influenza (flu) virus – Capable of mutation Changes 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 Bacteria – mutate - antibiotic resistance (e.g. MRSA); ineffective vaccines

9. Malaria – vaccines Loss of immunity on leaving a malarial area No repeat infections – no further exposure to Ag – no booster Lose immunological memory – limited life for memory cells – reduced number of memory cells No 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

10. 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 bacteria Penicillin – antibacterial – from Penicillium (fungus) Quinine – antimalarial – Cinchona tree Insulin (hormone) – antidiabetic – pigs; cows Enzymes – pancreatic – for CF – from animals Aspirin – analgesic / antiinflammatory - bark of willow tree Tamoxifen – anticancer – Pacific Yew tree Cinnamon – antidiabetic Star anise – Tamiflu – antiviral – from shikimic acid

13. 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 complications When people have a disease and the effects of the toxin must be ameliorated. Boyulinum antitoxin Diphtheria antitoxin Immune globulin (poled human antibodies) – prophylaxis; immunodeficiency disorders Rabied immune globulin Tetanus immune globulin Antivenom antibodies (spiders; snakes; scorpions; ticks; caterpillars; jellyfish Preparation Inject Ag (toxin) into animal – produces antibodies – antibodies harvested – must conform to WHO standards prior to use