2_Basics of surveillance of Adverse events following immunisation
- 1. AEFI BASICS Adverse events following immunization
- 2. An adverse event following immunization (AEFI) is any untoward medical occurrence which follows immunization and which does not necessarily have a causal relationship with the usage of the vaccine The adverse event may be any unfavorable or unintended sign (e.g. Abscess following vaccination), abnormal laboratory finding (e.g. Thrombocytopenia following measles vaccination) symptom or disease (e.g. Disseminated BCG infection following BCG vaccination). Definition of AEFI
- 3. 1 Vaccine product- related reaction An AEFI that is caused or precipitated by a vaccine due to one or more of the inherent properties of the vaccine product. 2 Vaccine quality defect-related reaction An AEFI that is 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. 3 Immunization error-related reaction An AEFI that is caused by Inappropriate vaccine handling, prescribing or administration . 4 Immunization anxiety- related reaction An AEFI arising from anxiety about the immunization. 5 Coincidental event An AEFI that is caused by something other than the vaccine product, immunization error or immunization anxiety WHO cause specific definition of AEFIs
- 4. Examples 1 Vaccine product-related reaction EXAMPLE Extensive limb swelling following DTP vaccination. 2 Vaccine quality defect-related reaction EXAMPLE Failure by the manufacturer to completely inactivate a lot of inactivated polio vaccine leads to cases of paralytic polio. 3 Immunization error-related reaction EXAMPLE Transmission of infection by contaminated multidose vial. 4 Immunization anxiety-related reaction EXAMPLE Vasovagal syncope in an adolescent following vaccination. 5 Coincidental event EXAMPLE A fever occurs at the time of the vaccination (temporal association) but is in fact caused by malaria.
- 5. 4 Immunization anxiety-related reaction 5 Coincidental event 3 Immunization error-related reaction Vaccine reactions 1 Vaccine product-related reaction EXAMPLE Extensive limb swelling following DTP vaccination. 2 Vaccine quality defect-related reaction EXAMPLE Failure by the manufacturer to completely inactivate a lot of inactivated polio vaccine leads to cases of paralytic polio. MINOR REACTIONS SEVERE REACTIONS
- 6. Vaccine reactions SEVERE REACTIONS MINOR REACTIONS Usually occur within a few hours of injection. Resolve after short period of time and 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). 2 Vaccine quality defect-related reaction 1 Vaccine product-related reaction
- 7. Pain Swelling Redness at injection site Local Minor reactions Fever Irritability Malaise Systemic
- 8. Vaccine reactions SEVERE REACTIONS MINOR REACTIONS Caused when recipient’s immune system reacts to antigens contained in the vaccine. Immune response to the vaccine's antigen can cause local and systemic reactions: - E.g. pain, fever, swelling, loss of appetite Other vaccine components can also trigger reactions - E.g. adjuvants, stabilizers, preservatives A "good" vaccine keeps even minor reactions to a minimum, while producing best possible immune response. Minor vaccine reactions are part of the body’s immune system and occur more often than severe, but usually heal. 2 Vaccine quality defect-related reaction 1 Vaccine product-related reaction
- 9. SEVERE REACTIONS MINOR REACTIONS Minor vaccine reactions, treatments and rates associated with childhood vaccines Vaccine Local reactions Systemic reactions (pain, swelling, redness) Fever > 38°C Irritability, malaise and systemic symptoms BCG1 90% – 95% – – Hepatitis B Adults up to 15%, Children up to 5% 1 – 6% – Hib 5 – 15% 2% – 10% Measles/MR/MMR ~ 10% 5% – 15% 5% (Rash) OPV None Less than 1% Less than 1%2 Pertussis (DTwP)3 up to 50% up to 50% up to 55% Pnemucoccal conjugate5 ~ 20% ~ 20% ~ 20% Tetanus/DT/aTd ~ 10%4 ~ 10% ~ 25%
- 10. Vaccine reactions MINOR REACTIONS SEVERE REACTIONS Usually do not result in long-term problems. Can be disabling. Are rarely life threatening. Include seizures and allergic reactions caused by the body's reaction to a particular component in a vaccine. 2 Vaccine quality defect-related reaction 1 Vaccine product-related reaction
- 11. What is the difference between serious and severe reactions?
- 12. Serious and severe reactions • Can be disabling and, rarely, life threatening • Most do not lead to long-term problems • Must be reported • Examples of severe reactions include non- hospitalized cases of- anaphylaxis that has recovered, high fever( >102 degree F), hypotonic hyporesponsive episodes, sepsis etc Severe reactions Any untoward medical occurrence that at any dose: Results in death. Requires inpatient hospitalization. Results in persistent or significant disability. AEFI cluster Serious reactions
- 13. Vaccine reactions MINOR REACTIONS SEVERE REACTIONS Severe vaccine reactions, treatments and rates associated with childhood vaccines Vaccine Reaction* Onset interval Frequency per doses given BCG Fatal dissemination of BCG infection 1 – 12 months 0.19 – 1.56/1.000.000 OPV Vaccine associated paralytic poliomyelitis (VAPP)** 4 – 30 days 2 – 4/1.000.000 DTwP Prolonged crying and seizures*** 0 – 24 hours < 1/100 HHE 0 – 24 hours < 1/1.000 – 2/1.000 Measles Febrile seizures 6 – 12 days 1/3.000 Thrombocytopenia 15 – 35 days 1/30.000 Anaphylaxis 1 hour 1/100.000 * Reactions (except anaphylaxis) do not occur if already immune (90% of those receiving a second dose); children >6 years unlikely to have febrile seizures. ** VAPP risk higher for first dose (1 in 750 000 compared with 1 in 5.1 million for subsequent doses), and for adults and immunocompromised clients. *** Seizures are mostly febrile. The risk of having a seizure depends on the persons age. The risk is much lower in infants <4 months of age. 2 Vaccine quality defect-related reaction 1 Vaccine product-related reaction
- 14. Vaccine reactions MINOR REACTIONS SEVERE REACTIONS EXAMPLE: OPV and vaccine associated paralytic poliomyelitis (VAPP) VAPP is a very rare event occurring 2–4 per every 1 million doses of OPV. VAPP (paralysis) can occur in a vaccinated child or persons in close contact to the child. VAPP can be proven by lab test in clinical case of polio. Depending on presence of wild polio, the risk of VAPP has to be weighed against benefit of vaccination: Risk of VAPP greater than risk of wild polio Risk of VAPP very much lower than risk of polio by natural infection. If wild poliovirus circulates If wild poliovirus no longer circulates 2 Vaccine quality defect-related reaction 1 Vaccine product-related reaction
- 15. Can you remember the 5 AEFI categories?
- 22. 1 Vaccine product-related reaction EXAMPLE Extensive limb swelling following DTP vaccination. 2 Vaccine quality defect-related reaction EXAMPLE Failure by the manufacturer to completely inactivate a lot of inactivated polio vaccine leads to cases of paralytic polio. 3 Immunization error-related reaction EXAMPLE Transmission of infection by contaminated multidose vial. 4 Immunization anxiety-related reaction EXAMPLE Vasovagal syncope in an adolescent following vaccination. 5 Coincidental event EXAMPLE A fever occurs at the time of the vaccination (temporal association) but is in fact caused by malaria.
- 23. Immunization error 1 Vaccine product-related reaction 2 Vaccine quality defect-related reaction 3 Immunization error-related reaction EXAMPLE Transmission of infection by contaminated multidose vial. 4 Immunization anxiety-related reaction 5 Coincidental event
- 24. What are potential causes for immunization errors?
- 25. What are potential causes for immunization errors? Non sterile injection Reconstitution error Injection at incorrect site Vaccine transported/ stored incorrectly Contraindication ignored
- 26. Non-sterile injection Immunization errors Reuse of disposable syringe or needle leading to contamination of the vial, especially in multi-dose vials. Improperly sterilized syringe or needle. Contaminated vaccine or diluent. Immunization error 3 Immunization error-related reaction Immunization errors Reuse of disposable syringe or needle leading to contamination of the vial, especially in multi-dose vials. Improperly sterilized syringe or needle. Contaminated vaccine or diluent Possible AEFI Infections, such as: Local injection site reactions. Toxic shock syndrome. Blood-borne transmission of disease. Death.
- 27. Reconstitution error Immunization errors Inadequate shaking of vaccine. Reconstitution with incorrect diluent. Other drug substituted for vaccine or diluent. Reuse of reconstituted vaccine at subsequent session. Immunization error 3 Immunization error-related reaction Immunization errors Inadequate shaking of vaccine. Reconstitution with incorrect diluent. Other drug substituted for vaccine or diluent. Reuse of reconstituted vaccine at subsequent session Possible AEFI Local abscess. Vaccine ineffective.* Effect of drug (e.g., insulin, oxytocin, muscle relaxants). Toxic shock syndrome. Death. * ineffective vaccine is not strictly an adverse event; it is a vaccine failure.
- 28. Injection at incorrect site Immunization errors BCG given subcutaneously. DTP/DT/TT applied too superficially. Injection into buttocks. Immunization error 3 Immunization error-related reaction Immunization errors BCG given subcutaneously. DTP/DT/TT applied too superficially. Injection into buttocks. Possible AEFI Local reaction or abscess or other local reaction. Local reaction or abscess or other local reaction. Sciatic nerve damage.
- 29. Vaccine transported/stored incorrectly Immunization errors Freezing vaccine during transport. Failure to keep vaccine in cold chain, exposing to excessive heat or cold. Immunization error 3 Immunization error-related reaction Immunization errors Freezing vaccine during transport. Failure to keep vaccine in cold chain, exposing to excessive heat or cold. Possible AEFI Increased local reaction from frozen vaccine. Ineffective vaccine.* * ineffective vaccine is not strictly an adverse event; it is a vaccine failure.
- 30. Contraindication ignored Immunization errors Vaccination staff ignoring or not becoming familiar with contraindications for a vaccine. Immunization error 3 Immunization error-related reaction Immunization errors Vaccination staff ignoring or not becoming familiar with contraindications for a vaccine Possible AEFI Avoidable severe reaction
- 31. How do you define a cluster of adverse events?
- 32. Definition of Clusters of events Clusters of events is two or more cases of the same adverse event related in time, place or vaccine administered. Clusters can be usually associated within: a particular provider or health facility a vial/vials of vaccine that has/have been Inappropriately prepared Contaminated Inappropriately stored (e.g. freezing vaccine during transport). Immunization error 3 Immunization error-related reaction
- 33. Immunization anxiety-related reactions 1 Vaccine product-related reaction 2 Vaccine quality defect-related reaction 3 Immunization error-related reaction 4 Immunization anxiety-related reaction EXAMPLE Vasovagal syncope in an adolescent following vaccination. 5 Coincidental event
- 34. Four anxiety-related reactions 4 Immunization anxiety-related reaction Fainting Fainting is relatively common, but usually only affects older children and adults. Fainting does not require any management beyond giving the injection while patients are seated (to avoid injury caused by falling) and placing the patient in a recumbent position after the injection. Hyperventilation Hyperventilation as a result of anxiety about immunization can cause light-headedness, dizziness, tingling around the mouth and in the hands. Vomiting Younger children tend to react differently, with vomiting a common anxiety symptom. Breath- holding may occur, which can end in a brief period of unconsciousness, during which breathing resumes. They may also scream to prevent the injection or run away. Convulsions An anxiety reaction to injection can, in rare cases, include convulsions.
- 35. Coincidental events 1 Vaccine product-related reaction 2 Vaccine quality defect-related reaction 3 Immunization error-related reaction 4 Immunization anxiety-related reaction 5 Coincidental event EXAMPLE A fever occurs at the time of the vaccination (temporal association) but is in fact caused by malaria.
- 36. Coincidental events require rapid follow up Coincidental events are inevitable when vaccinating children, especially during a mass campaign Expected coincidental events can be estimated by evaluating: – Normal incidence of disease and death in this age group – Coverage and timing of immunizations. Immediate investigation is critical to: – Respond to community’s concern about vaccine safety – Maintain public confidence in immunization 5 Coincidental event
- 37. Country Infant Mortality rate/1000 live births Number of births per year Estimated number of infant death in Estimated number of PVV/DTP immunizations* in (IMR) (N) a month a week a day a month a week a day Bhutan 42 15,000 53 12 2 3,233 746 106 Canada 5 3,88,000 162 37 5 86,864 20,045 2,856 China 13 16,364,000 17,728 4,091 583 3,634,035 8,38,624 1,19,475 India 47 27,098,000 1,06,134 24,492 3489 5,810,489 1,340,882 191,030 Indonesia 25 4,331,000 9,023 2,082 297 9,50,113 2,19,257 31,237 Expected coincidental deaths following DTP/PVV vaccination in selected countries
- 38. THANK YOU
Editor's Notes
- #2: Main idea: Ensure participants know the official definition of AEFI and break down the important aspects. Although all vaccines used in NIPs are safe and effective if used correctly, no vaccine is completely risk-free and adverse events will occasionally result after an immunization. Official definition: An adverse event following immunization (AEFI) is any untoward medical occurrence which follows immunization and which does not necessarily have a causal relationship with the usage of the vaccine. The adverse event may be any unfavourable or unintended sign, abnormal laboratory finding, symptom or disease. AEFIs are divided into five classifications.
- #4: Main idea: Explain different categories of AEFIs, using definitions below and the examples on the slide. Vaccine product-related reaction An AEFI that is caused or precipitated by a vaccine due to one or more of the inherent properties of the vaccine product. Vaccine quality defect-related reaction An AEFI that is 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. Immunization error-related reaction An AEFI that is caused by inappropriate vaccine handling, prescribing or administration and thus by its nature is preventable. Immunization anxiety-related reaction An AEFI arising from anxiety about the immunization.. Coincidental event An AEFI that is caused by something other than the vaccine product, immunization error or immunization anxiety.
- #5: Main message: Vaccine reactions can be classified into minor and severe reactions. A vaccine reaction is an individual's response to the inherent properties of the vaccine, even when the vaccine has been prepared, handled and administered correctly. There is low public tolerance of vaccine adverse reactions, so vaccines are only licensed when the frequency of severe reactions is very rare and when only minor, self-limiting reactions are reported.
- #6: Main idea: review minor reactions Usually occur within a few hours of injection. Resolve after a short period of time and pose little danger. Are often local (including pain, swelling or redness at the site of injection) or systemic (including fever, malaise, muscle pain, headache or loss of appetite). Parents should report any reaction that persists to a health worker.
- #7: Answer: See above, a non-exhaustive list.
- #8: Main message: Minor vaccine reactions usually occur more often than severe, but usually heal off completely. They are often part of the body’s immune system. Ideally vaccines will cause no, or only minor (i.e. non-severe) adverse reactions. Vaccination induces immunity by causing the recipient's immune system to react to antigens contained in the vaccine. Local and systemic reactions such as pain or fever can occur as part of the immune response. Other vaccine components (e.g. adjuvants, stabilizers, and preservatives) can trigger reactions. A successful vaccine keeps even minor reactions to a minimum while producing the best possible immune response.
- #9: Main idea: Review common reactions, treatments, and rates associated with childhood vaccines. The frequency of vaccine reactions likely to be observed with some of the most commonly used vaccines, and their treatments, are listed in the table. These reactions typically occur within a day or two of immunization (except for rash reactions after vaccine containing measles, which can arise up to 6 to 12 days after immunization) and persist from 1 to a few days. As can be seen from the table, the treatment is fairly simple and should be communicated to the patients parents by the health personnel for treatment of the patient at home. Local reactogenicity varies from one vaccine brand to another, depending on the strain and the number of viable antigen in the vaccine. Diarrhoea, Headache and/or muscle pains. When compared with whole cell pertussis (DTwP) vaccine, acellular pertussis (DTaP) vaccine rates are lower. Rate of local reactions are likely to increase with booster doses, up to 50 – 85%. Source: http://www.cdc.gov/vaccines/pubs/ACIP-list.htm Paracetamol dose: up to 15mg/kg every 6–8 hours, maximum of 4 doses in 24 hours.
- #10: Main message: review severe reactions Usually do not result in long-term problems. Can be disabling. Are rarely life threatening. Include seizures and allergic reactions caused by the body's reaction to a particular component in a vaccine. There is low public tolerance of vaccine adverse reactions, so vaccines are only licensed when the frequency of severe reactions is very rare and when only minor, self-limiting reactions are reported.
- #11: (Engage participants in a group discussion, encouraging them to voice their opinions. Answer is on next slide.)
- #12: Examples of severe reactions include unhospitalized cases of- anaphylaxis that has recovered, high fever( >102 degree F), acute flaccid paralysis, hypotonic hyporesponsive episodes, sepsis etc
- #13: Main idea: Review common reactions, treatments, and rates associated with childhood vaccines. The table lists frequency of vaccine reactions likely to be observed with some of the most commonly used vaccines, and their treatments. Point out the importance of knowing the onset intervals for the various reaction types to the specific vaccines and how the frequency per dose given can potentially help doing vaccine background rates comparisons.
- #14: Main message: Example of VAPP occurring from OPV to illustrate how the risk of VAPP can increase depending on whether wild polio has been eradicated or not. A well-documented example of a vaccine-associated adverse reaction is vaccine associated paralytic poliomyelitis (VAPP). VAPP is a very rare event that occurs in about two to four in every million doses of oral polio vaccine (OPV) given. OPV is a live vaccine, containing an attenuated (weakened) version of the disease-causing poliomyelitis virus. The vaccine is given orally and causes a mild infection that creates immunity against the wild poliovirus. In very rare instances, OPV can cause paralysis (VAPP), either in the vaccinated child, or in a close contact (to be kept in mind when undertaking an investigation!). VAPP can be proven by a laboratory test that detects vaccine virus in a clinical case of polio. When cases of poliomyelitis exist in the population, risk of VAPP is very much less than the risk of acquiring polio by natural infection. In countries where there are no longer cases of wild polio, VAPP can become a greater risk than wild polio. In many countries where wild polio has been eliminated, programmes have switched to using inactivated (killed) polio vaccine (IPV) A more expensive vaccine that does not carry the risk of VAPP Must be injected by a trained health worker.
- #15: (Engage participants in a group discussion, encouraging them to voice their opinions on the issue and working out the main messages given in the answer slide.)
- #16: (Facilitator: This activity will provide a brief interruption in the presentation.) Use the 5 AEFIs listed on this slide for an quick break for a quick activity: Ask the participants to choose one of the AEFIs on the slide. They can write it down or just keep it in mind. Give an example of a reaction from one of the 5 types and ask those who chose the corresponding AEFI to stand up. After a few seconds (enough time for the participants to think this through and stand), ask one of the standing participants to reveal which AEFI they are representing. If they are wrong, ask another until the correct AEFI is revealed. Repeat this with at least one example for each of the 5 main AEFIs. The next slide shows some of the examples already illustrated to the participants, but feel free to use others.
- #17: (Facilitator: This activity will provide a brief interruption in the presentation.) Use the 5 AEFIs listed on this slide for an quick break for a quick activity: Ask the participants to choose one of the AEFIs on the slide. They can write it down or just keep it in mind. Give an example of a reaction from one of the 5 types and ask those who chose the corresponding AEFI to stand up. After a few seconds (enough time for the participants to think this through and stand), ask one of the standing participants to reveal which AEFI they are representing. If they are wrong, ask another until the correct AEFI is revealed. Repeat this with at least one example for each of the 5 main AEFIs. The next slide shows some of the examples already illustrated to the participants, but feel free to use others.
- #18: (Facilitator: This activity will provide a brief interruption in the presentation.) Use the 5 AEFIs listed on this slide for an quick break for a quick activity: Ask the participants to choose one of the AEFIs on the slide. They can write it down or just keep it in mind. Give an example of a reaction from one of the 5 types and ask those who chose the corresponding AEFI to stand up. After a few seconds (enough time for the participants to think this through and stand), ask one of the standing participants to reveal which AEFI they are representing. If they are wrong, ask another until the correct AEFI is revealed. Repeat this with at least one example for each of the 5 main AEFIs. The next slide shows some of the examples already illustrated to the participants, but feel free to use others.
- #19: (Facilitator: This activity will provide a brief interruption in the presentation.) Use the 5 AEFIs listed on this slide for an quick break for a quick activity: Ask the participants to choose one of the AEFIs on the slide. They can write it down or just keep it in mind. Give an example of a reaction from one of the 5 types and ask those who chose the corresponding AEFI to stand up. After a few seconds (enough time for the participants to think this through and stand), ask one of the standing participants to reveal which AEFI they are representing. If they are wrong, ask another until the correct AEFI is revealed. Repeat this with at least one example for each of the 5 main AEFIs. The next slide shows some of the examples already illustrated to the participants, but feel free to use others.
- #20: (Facilitator: This activity will provide a brief interruption in the presentation.) Use the 5 AEFIs listed on this slide for an quick break for a quick activity: Ask the participants to choose one of the AEFIs on the slide. They can write it down or just keep it in mind. Give an example of a reaction from one of the 5 types and ask those who chose the corresponding AEFI to stand up. After a few seconds (enough time for the participants to think this through and stand), ask one of the standing participants to reveal which AEFI they are representing. If they are wrong, ask another until the correct AEFI is revealed. Repeat this with at least one example for each of the 5 main AEFIs. The next slide shows some of the examples already illustrated to the participants, but feel free to use others.
- #21: (Facilitator: This activity will provide a brief interruption in the presentation.) Use the 5 AEFIs listed on this slide for an quick break for a quick activity: Ask the participants to choose one of the AEFIs on the slide. They can write it down or just keep it in mind. Give an example of a reaction from one of the 5 types and ask those who chose the corresponding AEFI to stand up. After a few seconds (enough time for the participants to think this through and stand), ask one of the standing participants to reveal which AEFI they are representing. If they are wrong, ask another until the correct AEFI is revealed. Repeat this with at least one example for each of the 5 main AEFIs. The next slide shows some of the examples already illustrated to the participants, but feel free to use others.
- #23: Main idea: Bring back to mind the definition of Immunization error-related reaction An AEFI that is caused by inappropriate vaccine handling, prescribing or administration and thus by its nature is preventable. Errors can result during: Vaccine preparation Handling Storage Administration Identifying and correcting Immunization errors is important to preventing AEFIs that detract from the benefit of the immunization programme! (Facilitator: mention to participants that this expression has been also previously called "Programme error")
- #24: (Engage participants in a group discussion, encouraging them to voice their opinions on the issue and working out the main messages given in the answer slide.)
- #25: Answer: See above a non-exhaustive list.
- #26: Main idea: Show example of immunization errors and their possible AEFIs. Select a few and invite participants to give examples.
- #27: Main idea: Show example of immunization errors and their possible AEFIs. Select a few and invite participants to give examples.
- #28: Main idea: Show example of immunization errors and their possible AEFIs. Select a few and invite participants to give examples.
- #29: Main idea: Show example of immunization errors and their possible AEFIs. Select a few and invite participants to give examples.
- #30: Main idea: Show example of immunization errors and their possible AEFIs. Select a few and invite participants to give examples.
- #31: (Engage participants in a group discussion, encouraging them to voice their opinions on the issue and working out the main messages given in the answer slide.)
- #32: Main message: Immunization errors can result in clusters of events. Immunization errors can result in a cluster of events defined as two or more cases of the same adverse event related in time, place or vaccine administered. These clusters are usually associated with: a particular provider or health facility, 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.
- #33: Main message: Anxiety-related reactions are not related to the vaccine, but to the fear of the injection. Individuals can react in anticipation to and as a result of an injection of any kind.
- #34: Main message: The likelihood of anxiety from these reactions can be reduced by: Clear explanations about the immunization and Calm, confident administration Fainting Is relatively common, but usually only affects older children and adults. Does not require any management beyond giving the injection while patients are seated (to avoid injury caused by falling) and placing the patient in a recumbent position after the injection. Hyperventilation Can cause light-headedness, dizziness, tingling around the mouth and in the hands. Vomiting Younger children tend to react differently, with vomiting a common anxiety symptom. Breath-holding may occur, which can end in a brief period of unconsciousness, during which breathing resumes. They may also scream to prevent the injection or run away. Convulsions In rare cases. These children do not need to be investigated but should be reassured.
- #35: Main message: Coincidental events occur after a vaccination has been given but are not caused by the vaccine or its administration.
- #36: Main message: Coincidental events require rapid follow up Coincidental events are inevitable when vaccinating children, especially during a mass campaign. Vaccinations are normally scheduled in infancy and early childhood, when illnesses are common and congenital or early neurological conditions become apparent. Expected number of coincidental events after immunization can be estimated by: Applying the normal incidence of disease and death in these age groups Calculation of the expected background rate of that event may be helpful in the investigation of an AEFI Understanding background mortality in the context of deaths that coincidentally follow vaccination is key when responding to AEFI reports. The coverage and timing of immunizations Immediate investigation of a severe adverse event attributed to a vaccine, but not causally related to it, is critical: To respond to a community's concerns about vaccine safety and Maintain public confidence in immunization.