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Aefi investigating & causality assessment
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Aefi investigating & causality assessment



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  • As an example, the following slides will demonstrate the approach and process to an AEFI investigation.
  • What is an adverse event following immunization (AEFI)? Although the vaccines in general use in national immunization programmes are extremely safe and effective, adverse events can occur following vaccine administration and no vaccine is perfectly safe. In addition to the vaccines themselves, the process of immunization is a potential source of adverse events. An adverse event following immunization (AEFI) is any adverse event that follows immunization that is believed to be caused by the immunization. Using this terminology allows description and analysis of the event without pre-judging causality. Immunization will naturally be blamed for any event that happens after immunization. Reported adverse events can either be true adverse events, i.e. really a result of the vaccine or immunization process, or coincidental events that are not due to the vaccine or immunization process but are temporally associated with immunization. For the purpose of these guidelines AEFIs are classified into five categories. Immunization can cause adverse events from the inherent properties of the vaccine ( vaccine reaction ), or some error in the immunization process ( programme error ). The event may be unrelated to the immunization, but have a temporal association ( coincidental event ). Anxiety-related reactions can arise from the pain of the injection rather than the vaccine. In some cases the cause of the AEFI remains unknown .
  • For those who are not aware, the WHO publication, “Surveillance of adverse events following immunization, Field guide for managers of immunization programmes,” (WHO/EPI/TRAM/93.02/REV.1) is an excellent resource book, as a guide for both the development of a national AEFI monitoring and reporting system as well as investigating an AEFI. If copies are required, contact WHO, EPI Programme, either in the respective WHO Regional Offices, or WHO/HQ, Geneva. The four “trigger events” listed above, and some add a fifth one -’Other severe or unusual medical incidents that may be thought to related to immunization,” are important indicators. The basic idea is have these “trigger” events built into a routine reporting system so that they act as triggers to fire a response when something is reported. Most routine EPI do not conduct systematic AEFI investigations on a regular basis unless there is an adverse (real or false) reported.
  • It is necessary for National Immunization Programmes to define their trigger events, the manner of reporting those events, and the process of responding when a trigger event actually is reported. It is essential to establish clear responsibilities among health workers at the local level, and at higher level, amongst public health experts and NIP programme functionaries. Health workers must be trained and must be given clear guidelines as to what is to be reported normally, what is to be considered abnormal and, in the event of an abnormal event occurring, what actions to take place, who to contact and to whom to pass on the information.
  • An AEFI investigation follows the same principles of investigation as any disease outbreak investigation. Of course, the actions will differ slightly at different stages.
  • The slide is self-explanatory
  • As an example, the following slides will demonstrate the approach and process to an AEFI investigation.
  • Example of investigation, continued….
  • Example of investigation continued….
  • The slide is self explanatory
  • This slide continues on the example of an AEFI investigation….
  • Example of AEFI investigation..cotd..
  • Example, contd… The point to be highlighted here is that investigation without corrective actions is not good enough. Investigation must lead to improvement in the manner in which future activities would be carried out. It is also an opportunity to provide field workers the chance to learn to conduct such investigation and also provide them hands-on training. The second point to be highlighted is that actions must NOT wait till investigation is complete. Patients are priority: treat them and make sure that all available support is given to them. Next is the general public or the parents. Give them enough information, show that you care about this as much as they do and that your interest in the welfare of their children is genuine and professional.
  • Programme Error and their Consequences
  • Finally, a surveillance system should be as flexible to make it more appropriate to changing needs. Evaluation of a surveillance system may not be necessary as an annual exercise, but periodically a group of experts must sit together to review the relevance and usefulness of the surveillance system and make changes, where appropriate or necessary.


  • 2. AEFI: An example of an AEFI investigation
    • Background
      • It is reported that following a measles campaign in a primary school in District X, several children had convulsions. It was widely rumoured that the measles injection was responsible for it
      • One child had an attack of fit half an hour after the immunization. Following this three other children had fainting spells in the same class. All recovered spontaneously although the child who had the first convulsion took longer to recover. Also, the first child sustained a minor cut on the forehead from the fall
      • Next day, five more children called in sick on grounds that they had also attacks of fits after the school
    • Definitions
    • Detecting and reporting AEFIs
    • Conducting a case investigation
    • Analysing and assessing AEFI data
    • Taking action
    • Measuring outcome
    • A medical incident that takes place after an immunization, causes concern, and is believed to be caused by immunization
    • Vaccine reaction - caused by vaccine’s inherent properties
    • Programme error - caused by error in vaccine preparation, handling, or administration
    • Coincidental - happens after immunization but not caused by it (a chance association)
    • Injection reaction - anxiety or pain of injection not vaccine
    • Unknown - cause cannot be determined
  • 5. CLUSTER
    • >=2 cases of the same adverse event following immunizations related in time, geography or in the vaccine administered
      • Why is it important to monitor for clustering ?
    • Detect, correct, and prevent programme errors
    • Identify problems with vaccine lots or brand
    • Prevent false blame from coincidental events
    • Maintain confidence by properly responding to parent/community concerns while increasing awareness (public and professional) about vaccine risks
    • Generate new hypotheses about vaccine reactions that are specific to the population
    • Estimate rates of occurrence on AEFI in the local population, compared with trial and international data (particularly for new vaccines being introduced)
    • Decide on
      • WHICH events to be included in surveillance?
      • WHO should be involved in detection?
      • WHAT is the route of reporting?
      • WHEN should AEFIs be reported?
      • HOW should reporting occur?
      • WHAT happens next?
  • 9. AEFI
    • Detection and reporting
      • Every individual that administers an immunization injection should know about AEFI
      • The following are events need to be reported and investigated immediately
        • All deaths suspected to be related to immunization
        • All hospitalisation suspected to be related to immunization
        • Any event where vaccine quality is suspected
  • 10. AEFI
    • Detection and reporting
      • The above basic categories act as “ trigger ” mechanisms for further course of action
      • While minor events may be recorded and reported as a routine activity in monthly reports to be analysed only at periodic times, sudden, unexplained deaths or large scale hospitalisation or a cluster of events reported following immunisation warrants immediate investigation
  • 11. Reporting of Severe AEFI
  • 12. AEFI
    • Investigation
      • AEFI investigation will attempt to
        • confirm or propose alternative diagnosis of the reported event
        • identify the specifications of the vaccine incriminated
        • examine the operational aspects of the programme
        • identify whether it was an isolated event or a cluster of events and, if a cluster, where the immunization was given and what vaccines were used
      • Preliminary investigation may be carried out by the local health worker, but serious AEFIs or clusters of AEFIs should be investigated from district or state/central level
  • 13. AEFI
    • Investigation
      • Data on the patient(s); vaccine (lot number, expiry, manufacturer, lab results if any), storage, reconstitution practice, diluent used, general disease information in the area, similar disease episodes in unimmunized persons in the same locality, etc. should be collected
      • Collect samples of vaccines and diluents used (make sure vaccine sample collected are kept in the cold chain)
    • The reporting of the minor events is done on monthly basis in the form 9 of RCH
    • The reporting for severe cases is done using First Information report (FIR) in 48 hrs
    • Followed by Preliminary investigation report (PIR) within 7 days
    • And a Final report in form of Detailed investigation report (DIR) within 90 days
  • 15. AEFI: An example of an AEFI investigation
    • Background
      • It is reported that following a measles campaign in a primary school in District X, several children had convulsions. It was widely rumoured that the measles injection was responsible for it
    • Hypothesis
      • that the reported health event (convulsion) was an AEFI following measles vaccination
    • Define the case
      • You define your ‘case’ as any child in that primary school who received measles injection on that particular day and had convulsions .
  • 16. AEFI: example contd..
    • Case investigation
      • Line list all children, with age & sex, who had received measles injection on that day
      • Find those that reported to have had convulsions
      • Find out all the details regarding the convulsions- onset time after immunization, manner of convulsion, recovery following the convulsion, concomitant medications, fever, any other health problems. Determine the quality of the vaccine (expiry, storage), reconstitution, diluent, injection process, etc.
      • Take samples of the vaccine vials used for lab testing
      • Scrutinise the stock entries, stock balance, etc.
  • 17. AEFI: example contd..
      • One child had an attack of fit half an hour after the immunization. Following this three other children had fainting spells in the same class. All recovered spontaneously although the child who had the first convulsion took longer to recover. Also, the first child sustained a minor cut on the forehead from the fall
      • Next day, five more children called in sick on grounds that they had also attacks of fits after the school
  • 18. AEFI
    • Data analysis
      • Once the data is collected, it should be analysed as quickly as possible to determine whether the AEFI is
        • Programme related (incorrect dose of vaccine, wrong site, wrong diluent, improper storage & handling, use of other medicines as diluent, etc.)
        • Vaccine induced AEFI
        • Coincidental AEFIs (caused by something other than vaccine or programme errors)
        • Unknown
      • Laboratory support
        • If patient hospitalised, tests may confirm diagnosis
        • Testing vaccines often yield doubtful answers
        • Send case investigation report with vaccine for test
  • 19. AEFI: example contd..
    • Data Analysis
      • You find that the vaccine used has not expired, was well maintained in the cold chain, correct diluent was used,
      • There was no evidence of contamination, the health workers always discarded reconstituted vaccine at the end of the session.
      • The medical history showed that the fits which the other children had were mere fainting spells, lasting only for a few moment, with spontaneous recovery. No subsequent attacks occurred
      • The index child had a true convulsion. No fever or other illnesses at that time.
  • 20. AEFI: example contd..
      • However, going over the medical history of the child, the health worker recalled that last year the same child had an episode of convulsion for which he had provided treatment. He had advised that the parents should consult a medical or a neurological expert for further management. On questioning, it was found that the parents did not have the time or the money to do that and it was felt that it would resolve naturally
  • 21. AEFI: example contd..
    • Conclusion
      • From the available information, and based on the data analysis, you conclude that event was not an AEFI, but Coincidental.
      • Following this, you will take time to explain to the parents, teachers and the community about the event, your investigation and your final conclusions.
  • 22. AEFI
    • Corrective and other actions
      • Action must not wait for investigation to be completed
      • Treat the patient(s) as the first response
      • Communicate, inform the public, parents, media people on the event, actions being taken & next steps
      • Once the investigation is completed, publicise the results
      • Take corrective actions, where necessary
      • Training of health workers & supervision to prevent avoidable AEFIs in future
  • 23. AEFI
    • Avoiding Programme Errors
      • Use sterile needle & syringe for every injection
      • Reconstitute only with specific diluent
      • Discard reconstituted vaccines after six hours
      • Do not store drugs & other medicines in the same fridge as the vaccines and diluents
      • Train & supervise health workers to ensure safe injection practices
      • Monitor, Investigate and Act when AEFIs occur
  • 24. AEFI
    • Evaluation
      • Like any other surveillance systems, AEFI surveillance must also be evaluated periodically to examine its usefulness and to modify it if necessary
      • Issues to consider when evaluating a surveillance system are
        • timeliness, completeness, accuracy of the system
        • swiftness with which response was effected when a trigger event was reported
        • appropriateness of actions taken
        • potential for strengthening of immunization system
  • 25. IDENTIFYING CAUSE OF AEFI CLUSTER Yes Yes Yes Yes Yes Yes No No No No No No Programme error, coincidental or vaccine problem/ “unknown” Manufacturer error, batch problem, or transport/storage error Programme error Coincidental event Vaccine reaction Cluster of AEFIs All cases from only one facility (same lot used at others)? Coincidental event Programme error or vaccine problem All cases got same vaccine or lot? Known vaccine reaction? Similar illness in others who didn’t get vaccine? Similar illness in others who didn’t get vaccine? Rate of reaction within the expected rate?
  • 26. CAUSALITY ASSESSMENT ? Adverse Event
    • Risk evaluation requires a 2x2 table of exposures and outcomes
    • Case reports represent only one cell of table
    • Risk of event from vaccine = a*d/b*c
    • Immunization safety is likely to become increasingly important
    • Need to develop system which
      • detects
      • investigates
      • takes action (including communication)
      • measures outcome of action