A vaccine is biological preparation that improves immunity to a particular disease, a vaccine typically contains a disease causing micro-organisms often weakened or killed.

 No vaccine is 100% effective! Most that are used in North America are between 70 and 95% effective  Vaccines provide both Individual benefit and a Public health benefit.  “herd immunity”

Mummies China/India Crusaders W Europe: fatality rate 25% History changed:  Cortes  Louis XIV

 Vaccination Jenner 1796 : Cowpox/Swinepox 1800’s Compulsory childhood vaccination 1930’s Last natural UK case 1940’s last natural US case 1958 WHO program October 1977: Last case (Somalia)

 No animal reservoir  Lifelong immunity  Rare Subclinical cases  Infectivity does not precede overt symptoms  One Variola serotype  Effective vaccine  Major commitment by governments

 DiseaseTransmissionR0[N]Herd immunity threshold  Diphtheria Saliva6-785% Diphtheria  MeaslesAirborne % Measles  MumpsAirborne droplet % Mumps  PertussisAirborne droplet % Pertussis  PolioFecal-oral route % Polio  RubellaAirborne droplet % Rubella  SmallpoxSocial contact % Smallpox ^^ - R0 is the basic reproduction number, or the average number of secondary infectious cases that are produced by a single index case in completely susceptible population.basic reproduction number

PROPHYLACTIC THERAPEUTIC  Prevent future infection by any means. e.g. to prevent or ameliorate the effects of a future infection by any natural or "wild" pathogen). infectionpathogen  Prevent severity of infection problems already occurred. e.g. vaccines against cancer are also being investigated.

Separate two effects of organism Formalin can be used Use antigen part of virus Attenuate virus aging altering or mutating Toxins of toxoid vaccines are treated with aluminum

Live, attenuated vaccine Measles, mumps, rubella, polio (Sabin vaccine), yellow fever Inactivated or “killed” vaccine Cholera, flu, hepatitis A, Japanese encephalitis, plague, polio (Salk vaccine), rabies Toxoid vaccineDiphtheria, tetanus Subunit vaccinesHepatitis B, pertussis, pneumonia caused by Streptococcus pneumoniae Conjugate vaccinesHaemophilus Influenza type B, pneumonia caused by Streptococcus pneumoniae DNA vaccinesIn clinical testing Recombinant vector vaccines In clinical testing

 ATTENUATION is usually achieved by passage of the virus in foreign host such as embryonated eggs or tissue culture cells.  These tend to be less virulent for the original host. In Sabin polio vaccine, attenuation was only achieved with use of high inocula and rapid passage in primary monkey kidney cells.  The viruses became overgrown with a less virulent strain (for humans) that could grow well in non- nervous tissue but not in CNS. Non-virulent strains of all three polio types produced for the vaccine.

Polysacchar ide coat Bacteriu m toxoid Currently, conjugate vaccines are available to protect against a type of bacterial meningitis caused by Haemophilus influenzae type b (Hib). Meningitis, an inflammation of the fluid-filled membranes that protect the brain and spinal cord, can be fatal, or it can cause severe, life-long disabilities such as deafness and mental retardation.

 The deliberate introduction of a DNA plasmid carrying a protein-coding gene that transfects  Cells in vivo at very low efficiency and expresses an antigen that causes an immune response.  These are often called DNA vaccines but would better be called DNA- mediated or DNA-based

 1) Plasmids are easily manufactured in large amounts  2) DNA is very stable  3) DNA resists temperature extremes so storage and transport are straight forward  4) DNA sequence can be changed easily in the laboratory. This means that we can respond to changes in the infectious agent

 1) Potential integration of plasmid into host genome leading to insertional mutagenesis  2) Induction of autoimmune responses (e.g. pathogenic anti-DNA antibodies)  3) Induction of immunologic tolerance (e.g. where the expression of the antigen in the host may lead to specific non-responsiveness to that antigen)