vaccine safety. vaccine-induced feline fibrosarcoma current estimate is: 27,000 vaccine induced...
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Vaccine-induced feline fibrosarcoma
• Current estimate is: 27,000 vaccine induced tumors expected per year• ‘93 1-2 per 10,000• ‘97 3.6 per 10,000• ‘98 up to 5 per 10, 000
Pathogenesis of vaccine injection site fibrosarcomas
• Injection triggers inflammation and release of platelet-derived growth factor
• Activation of sis oncogene occurs• Sarcoma develops at the site
Types of Adverse Responses
• Vaccine injection site fibrosarcomas• Hypersensitivity Type 1 – Anaphylaxis• Hypersensitivity Type 2- Cytotoxic • Hypersensitivity Type 3 - Immune complex • Hypersensitivity Type 4 - Granulomas• Autoimmune disease • Induction of disease/ increase in severity of disease/ reversion
to virulence
Type I Hypersensitivity
• Systemic Anaphylaxis• IgE mediated reaction• requires previous sensitization• sensitizing agent may be antigen, cross-reactive antigen, or other
proteins present in vaccine• factors to consider: adjuvant, genetics
Mechanism for type I reactions
HistamineECF-ALeukotrienes
Smooth muscle contractionVascular permeabilityVasodilationEosinophil Chemotaxis
Mast Cell
AgAg
Mechanism for systemic anaphylaxis
Induction of IgE by Vaccines
• Antigen itself• virus e.g. Bovine Respiratory Syncytial Virus• bacteria e.g. Hemophilus somnus
• Constituents of carrier• gelatin
• Impurities in antigen preparation• fetal bovine serum, ovalbumin
Examples of type I reactions to non-essential antigens• IgE responses to gelatin as a stabilizer: measles-mumps-
rubella vaccine, yellow fever vaccine, diptheria-tetanus-pertussis (DTP) vaccine, and DTaP (acellular pertussis)
• IgE responses to ovalbumin: yellow fever, influenza, measles, mumps
More Examples
• Horses vaccinated with egg-derived equine encephalitis vaccines• Cattle vaccinated with baby hamster kidney derived foot and mouth
disease vaccine• Humans vaccinated with human diploid cell line rabies vaccine• Cattle vaccinated with bovine respiratory syncytial virus vaccine
Type II Hypersensitivity
• IgG and/or IgM binding to cell-associated antigens
• Fixation of complement
• Cell lysis and/or phagocytosis
Mechanism of type II Reactions
Host target cell
Complement
Lysis of target cell
phagocytosis of target cell
Examples of type II reactions
• Immune-mediated hemolytic anemia has been associated with vaccination of dogs with combination vaccines
• Hemolytic anemia and thrombocytopenia have been associated with recombinant hepatitis B vaccine in humans
Type III Hypersensitivity
• Immune complex diseases• IgG binds antigen fixes complement and attracts neutrophils• Systemic form: arthritis, vasculitis, glomerulonephritis• Local form: Arthus-type lesions in skin or lung
Examples of type III reactions• Canine Adenovirus type 1 (hepatitis) vaccine-induced “Blue
eye”anterior uveitis• Local Arthus type skin reactions in all species within 24 hours of
vaccine• Serum sickness-like illness in humans after immunization with
human diploid cell rabies vaccine (vasculitis, arthritis)
Type IV Hypersensitivity
• Delayed type reaction (DTH), occurs within 48 to 72 hours after antigen administration
• Mediated by sensitized T lymphocytes• Indicates strong T helper 1 cell response• Local response shows erythema, induration
Examples of type IV reactions
• DTH reactions have been observed in humans after immunization with propionibacterium acnes autovaccine
• Children with non-anaphylactic reactions to gelatin-containing vaccine and increased lymphocyte stimulation to gelatin may have DTH reactivity
Examples of Vaccines Generated Autoimmunity
• Rabies vaccine-induced autoimmune encephalomyelitis • Association is suggested: for hepatitis B vaccine with
rheumatoid arthritis • Auto Immune Hemolytic Anemia (AIHA) in infant girl after
DPT and polio vaccination
Vaccine Mediated, Enhancement of Disease• Respiratory syncytial virus formalin-inactivated vaccine caused
severe RSV in vaccinated children• Bovine RSV formalin-inactivated vaccine caused disease
enhancement in BRSV vaccinated calves
Disease caused by vaccination
• Inadequate killing resulting in residual virulence e.g. formalin inactivated Salk polio virus in late 1950’s
• Immuno suppressed host, e.g. MLV in AIDS patient• Intrauterine infection of fetus after immunization of mother with MLV,
e.g. teratogenic effects with bluetongue virus
Summary
• Adverse effects of vaccines are rare• Killed vaccines with adjuvant are more likely to have
pathological sequel• Systemic anaphylaxis may result from sensitization to
components of the vaccine • Immunomodulation is an important factor in disease
development by vaccines
Importance of Vaccine Safety
• Decreased disease risks and increased attention on vaccine risks
• Public confidence in vaccine safety is critical• higher standard of safety is expected of vaccines• vaccinees generally healthy
(vs. ill for drugs)• vaccination universally recommended and mandated
Diphtheria 31,054 0 -100Measles 390,852 66 -99Mumps 21,342 314 -99Pertussis 117,998 25,616 -78Polio (wild) 4,953 0 -100Rubella 9,941 11 -99Cong. Rubella Synd. 19,177 1 -99Tetanus 1,314 27 -98Invasive Hib Disease 24,856 144 -99
Total 566,706 26,179 -95
Vaccine Adverse Events 0 15,803 +++
Disease Pre-vaccine Era 2005 % change
Comparison of Maximum and Current Reported Morbidity, Vaccine-Preventable Diseases and
Vaccine Adverse Events, United States
Prelicensure Human Studies
• Phases I, II, III trials• Common reactions are identified• Vaccines are tested in thousands of persons before being licensed
and allowed on the market
Postlicensure Surveillance
• Identify rare reactions• Monitor increases in known reactions• Identify risk factors for reactions• Identify vaccine lots with unusual rates or types of events• Identify signals
Postlicensure Vaccine Safety Activities
• Phase IV Trials • ~10,000 participants• better but still limited
• Large-Linked Databases
• Clinical Immunization Safety Assessment Network
Vaccine Adverse Event Reporting System
(VAERS)
• National reporting system• Jointly administered by CDC
and FDA• Passive (depends on healthcare providers and others to report)• Receives ~15,000 reports per year
Vaccine Adverse Event Reporting System
(VAERS) • Detects
• new or rare events• increases in rates of known side effects• patient risk factors
• Additional studies required to confirm VAERS signals
• Not all reports of adverse events are causally related to vaccine
Adverse Event Classification
• Vaccine-induced• Vaccine-potentiated• Programmatic error• Coincidental
Clinical Immunization Safety Assessment (CISA) Network• Improve understanding of vaccine safety issues at individual
level• Evaluate persons who experience adverse health events• Gain better understanding of events• Develop protocols for healthcare providers
Vaccine Injury Compensation Program (VICP)
• Established by National Childhood Vaccine Injury Act (1986)• “No fault” program• Covers all routinely recommended childhood
vaccines
The Provider’s Role
• Immunization providers can help to ensure the safety and efficacy of vaccines through proper:
• vaccine storage and administration• timing and spacing of vaccine doses• observation of contraindications and precautions
Invalid Contraindications to Vaccination
• Minor illness• Mild/moderate local reaction or fever following a prior
dose• Antimicrobial therapy• Disease exposure• Pregnancy or immunosuppression• Premature birth• Breastfeeding• Allergies to products not in vaccine• Family history (unrelated to immunosuppression)