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Immunization and AEFI
- 1. Immunization and Adverse Events Following Immunization Kayode Afolabi
- 2. Outline • Introduction • History of Immunization • Types of Vaccines • Vaccine dosages and routes • Adverse Events Following immunization • Confounders that may affect rates of AEFIs • Pattern of minor AEFIs in Nigeria • Conclusion
- 3. Introduction • Vaccination: process of administering/getting an agent • Immunization: both the process of administering/getting and the process of becoming immune • Vaccine: a weakened or killed microorganism or its product to stimulate the host’s immunologic response (injection or oral) • Prevents 2-3 million deaths every year (WHO) • Very cost-effective • However, vaccines are not completely risk-free and adverse events following immunization (AEFI) occur. • Low tolerance to AEFI because vaccines are given to healthy persons to prevent disease.
- 4. History of immunization • Over 2000 years ago in China and India - Inoculation with exudates of smallpox pustules • 1796 - Edward Jenner - Father of immunology used matter from cowpox pustules to inoculate patients successfully against smallpox • 1885 – Louis Pasteur – successfully vaccinated a boy with live attenuated rabies vaccine • 1967 – WHO’s Intensified Smallpox Eradication Programme (Africa and Asia) • 1974 – Expanded Programme on Immunization (WHO + UNICEF + GAVI Alliance) • Currently over 20 Vaccine Preventable Diseases
- 5. Expanded Programme on Immunization • Established by WHO in 1974 following success of the smallpox program • UNICEF joins in 1977 and GAVI Alliance set-up in 1999 • Initial goals: • To vaccinate children against six childhood diseases (i.e. tuberculosis, polio, diphtheria, pertussis, tetanus and measles) by the time they were one year of age • To give tetanus toxoid vaccinations to women to protect them and their newborns against tetanus • Now includes Hep B, Hib, Strep. Pneumoniae, Rotavirus. • Regionally: HPV, Meningococcal meningitis, yellow fever, dengue e.t.c
- 6. Type of Vaccines based on type of antigen
- 8. Vaccine dosages and routes Vaccine/Suppl ement Age Dose Route of administeration Vaccination Site BCG At birth or ASAP after birth 0.05 ml Intradermal Upper left arm HEP B At birth upto 24hrs 0.5 ml Intramuscular Outer part of right thigh OPV 6, 10 and 14 weeks 2 drops Oral Mouth PENTA 6, 10 and 14 weeks 0.5 ml Intramuscular Outer part of left thigh PCV 6, 10 and 14 weeks 0.5 ml Intramuscular Outer part of right thigh IPV 14 weeks 0.5 ml Intramuscular Outer part of right thigh. 2.5cm away from PCV site ROTA 6 and 10 weeks 1.5 ml Oral Mouth MEASLES 9 months and 15 months 0.5 ml Subcutaneous Upper left arm YELLOW FEVER 9 months 0.5 ml Subcutaneous Upper right arm VIT. A 9 months and 15 months 100,000 IU Oral Mouth
- 9. Adverse Events Following Immunization • any untoward medical occurrence that appears during/after immunization but not necessarily caused by the immunization • affect public trust in vaccine safety and in essence the performance of immunization programmes • Very Common: ≥ 1 in 10 • Common/frequent: 1 to < 10 in 100 • Uncommon/infrequent: 1 to < 10 in 1000 • Rare: 1 to < 10 in 10000 • Very rare: ≤ 1 in 100000
- 10. Adverse Events Following Immunization • Higher rates with 1st doses of multidose vaccines • 5 categories: • Vaccine product-related reaction • Vaccine quality defect-related reaction • Immunization error-related reaction • Immunization anxiety-related reaction • Coincidental events Vaccine reactions: Minor or Severe
- 11. Vaccine product-related reaction • caused or precipitated by a vaccine due to one or more of the inherent properties of the vaccine product. • Example: Extensive limb swelling following DTP vaccination
- 12. Vaccine quality defect-related reaction • caused or precipitated by a vaccine that is due to one or more quality defects of the vaccine product including its administration device as provided by the manufacturer. • Example: Failure by the manufacturer to completely inactivate a lot of inactivated polio vaccine leads to cases of paralytic polio.
- 13. Minor vaccine reactions • Occur within a few hours of injection • Resolve after short period of time • pose little danger • Local (includes pain, swelling or redness at the site of injection) • Systemic (includes fever, malaise, muscle pain, headache or loss of appetite). • Usually require little or no intervention
- 15. Severe vaccine reactions • Longer onset interval • may take a longer time to resolve • can be potentially serious/dangerous. • Serious: • results in death • life-threatening • requires in-patient hospitalization or prolongation of existing hospitalization, • results in persistent or significant disability/incapacity • congenital anomaly/birth defect • requires intervention to prevent permanent impairment or damage. • E.g. Vaccine Associated Paralytic Polio, seizures, allergic reactions (including anaphylaxis), thrombocytopenia, Hypotonic Hyporesponsive Episodes)
- 16. Some severe vaccine reactions (WHO)
- 17. Frequency and severity of adverse vaccine reactions
- 18. Immunization error-related reaction • caused by inappropriate vaccine storage, handling, preparation or administration and thus by its nature is preventable. • Example: Transmission of infection by contaminated multidose vial. • Solitary or Cluster • Cluster: two or more cases of the same adverse event related in time, place or vaccine administered
- 20. Immunization anxiety-related reaction • arising from anxiety about the immunization • Commoner in older children/adolescents or adult • Example: Vasovagal syncope in an adolescent during/following vaccination.
- 22. Coincidental events • caused by something other than the vaccine product, immunization error or immunization anxiety. • Example: A fever occurs at the time of the vaccination but is in fact caused by malaria • Illnesses and congenital conditions around the time of routine vaccinations • The background rates of such events is deducted from the observed rate to determine actual vaccine/immunization related reactions
- 24. Confounders that may affect rates of AEFIs • Vaccines • Age • Vaccine doses • Case definitions • Surveillance methods
- 25. Pattern of minor AEFIs in Nigeria Study Title, Location and Year Author Prevalenc e of fever Prevalence of Pain and/or swelling Other findings Pattern of adverse events following immunization in nourished and malnourished infants in Kano, North- Western Nigeria 2016 UM Lawan et al 79.8% nourished and 95.2% malnourishe d infants 29.3% nourished and 47.6% malnourished infants • Majority of the AEFI experienced (58.7%, and 52.4%) occurred within 1–11hr • 99.1% and 100% were mild to moderate in severity Adverse events following immunization: Knowledge and experience of mothers in immunization centres in Enugu State, Nigeria 2009 OC Ekwueme 90.4% 27.7% • rashes and convulsion 2.7% • 93.2% of these reactions occurred within 24 hours.
- 26. Conclusion • Immunization is one public health intervention that has had a very significant impact on morbidity and mortality reduction. • Vaccines like other pharmaceutical products have adverse effects. Adverse Effects Following Immunization are not as common as reported and most of the actual AEFIs are minor and usually resolve on their own. • These can reduce the acceptance of immunization if immunization programmes are not properly managed.
- 27. Sources • WHO. 2019. WHO COURSE ON VACCINE SAFETY BASICS Retrieved from https://vaccine-safety-training.org/overview-and-outcomes- 3.html • Muhammad LU et al. Pattern of adverse events following immunization in nourished and malnourished infants in Kano, North- Western Nigeria. Sahel med. J. 2016; 19 (3): 131-136 • Ekwueme OC. Adverse events following immunization: Knowledge and experience of mothers in immunization centres in Enugu State, Nigeria. Int. J. Med. and Hlth. Dvlpt. 2009; 14 (1):
- 28. Further reading on Immunization • Passive and active immunization • OPV vs IPV • Herd Immunity • Supplemental and routine vaccination • VVM and cold chain • Number of doses per vial of vaccines and implications • Missed opportunities and management of late presenters • Cut-offs for Immediate vs late AEFIs
Editor's Notes
- One of the most cost-effective interventions of Public Health. With the exception of safe water, nothing else, not even antibiotics, has had such a major effect on the reduction of mortality (deaths) and morbidity (illness and disability) and on population growth.
- In 1796, he carried out his now famous experiment on eight-year-old James Phipps. Jenner inserted pus taken from a cowpox pustule and inserted it into an incision on the boy's arm. He was testing his theory, drawn from the folklore of the countryside, that milkmaids who suffered the mild disease of cowpox never contracted smallpox, one of the greatest killers of the period, particularly among children. Jenner subsequently proved that having been inoculated with cowpox Phipps was immune to smallpox. He submitted a paper to the Royal Society in 1797 describing his experiment, but was told that his ideas were too revolutionary and that he needed more proof. Undaunted, Jenner experimented on several other children, including his own 11-month-old son. In 1798, the results were finally published and Jenner coined the word vaccine from the Latin 'vacca' for cow. Pasteur discovered how to make vaccines by attenuating, or weakening, the microbe involved following his investigations with fowls and fowl cholera and extended the procedure to Anthrax successfully protecting Sheeps, Cows and goats against the disease by administering the attenuated vaccines. Pasteur then wanted to move into the more difficult area of human disease, in which ethical concerns weighed more heavily. He looked for a disease that afflicts both animals and humans so that most of his experiments could be done on animals, although here too he had strong reservations. Attenuation of rabies was first achieved in monkeys and later in rabbits. Meeting with success in protecting dogs, even those already bitten by a rabid animal, on July 6, 1885, Pasteur agreed with some reluctance to treat his first human patient, Joseph Meister, a nine-year-old who was otherwise doomed to a near-certain death. Success in this case and thousands of others convinced a grateful public throughout the world to make contributions to the Institut Pasteur. It was officially opened in 1888 and continues as one of the premier institutions of biomedical research in the world. Its tradition of discovering and producing vaccines is carried on today by the pharmaceutical company Sanofi Pasteur.
- Based on the emerging success of the smallpox programme, Dr Donald A Henderson of WHO came up with the idea that a similar approach could be taken with other vaccine-preventable diseases and in 1974, the World Health Organization (WHO) launched the Expanded Programme on Immunization (EPI). Initially, there were issues with funding and staffing and hence productivity until 1977 Dr Halfdan Mahler, the WHO Director-General at the time increased internal funding and James Grant of UNICEF, provided funding for national programmes and persuaded national leaders to support EPI. Immunization received a massive boost in 2000 with the launch of the GAVI Alliance, bringing together governments, international agencies, the private sector and philanthropic foundations
- Live vaccines use a weakened (or attenuated) form of the germ that causes a disease. Provide long-lasting immune response usually for a lifetime of protection against a germ and the disease it causes. Chance of causing the disease especially in immunosuppressed people. They are very thermolabile and require refrigerating/freezing. Examples of live-attenuated vaccines include Measles, mumps, rubella (MMR combined vaccine), Rotavirus, Smallpox, Chickenpox, Yellow fever vaccines. Killed or Inactivated vaccines: Inactivated vaccines use the killed version of the germ that causes a disease. Inactivated vaccines usually don’t provide immunity (protection) that’s as long lasting as live vaccines. Hence, the need for repeated doses/booster shots. Examples include Hepatitis A, Flu (shot only), IPV, Rabies vaccines. Subunit (cellular fraction, purified, recombinant, polysaccharide, and conjugate vaccines): Subunit, recombinant, polysaccharide, and conjugate vaccines use specific pieces of the germ — like its protein, sugar, or capsid (a casing around the germ). Very strong immune response because these vaccines use only the specific pieces of the germ enough to cause response. They can be used in immunosuppressed people. They may require booster shots. Examples include Hib (Haemophilus influenzae type b), Hepatitis B, HPV (Human papillomavirus), Whooping cough (part of the DTaP combined vaccine), Pneumococcal disease, Meningococcal disease, Shingles vaccines. Toxoid vaccines: Toxoid vaccines use a toxin (harmful product) made by the germ that causes a disease. They create immunity to the parts of the germ that cause a disease instead of the germ itself. That means the immune response is targeted to the toxin instead of the whole germ. They may require booster shots to get ongoing protection against diseases. Examples include Diphtheria and Tetanus toxoids.
- Immediate vs late AEFIs
- These reactions typically occur within a day or two of immunization (except for rash reactions after measles vaccine, which can arise up to 6 to 12 days after immunization) and persist from one to a few days. Local and systemic reactions such as pain or fever can occur as part of the immune response to the vaccine itself or other vaccine components (e.g. adjuvants, stabilizers and preservatives). Ideally vaccines will cause no, or only minor (i.e. non-severe), adverse reactions. A successful vaccine keeps even minor reactions to a minimum while producing the best possible immune response. Most vaccine reactions are minor.
- AEFI clusters are usually associated with a particular provider, health facility, and/or a vial of vaccine that has been inappropriately prepared or contaminated. Immunization errors can also affect many vials, for example, freezing vaccine during transport may result in an increase in local reactions
- Excluding coincidental events/background rates is particularly useful in comparison of AEFIs across different populations. Differences in background rates is a confounding factor that may mislead the investigator into wrongly concluding that a population with a higher observed rate has a higher rate of AEFIs.