Causality assessment is a procedure used to determine if there is a cause-and-effect relationship between a medicine/vaccine (considered the causative factor) and the occurrence of an adverse event, with no other factors intervening in the process.
The assessment of causality is a common procedure in pharmacovigilance. It is performed at different levels which include medical officers, investigators, and professionals working in drug safety department of a pharmaceutical company and national health authorities e.g. SAHPRA which can assist in making regulatory decisions.
Causality assessment is the key factor for:
- • Identification of new safety signals, and
- • Assessing whether the benefits of a medicine/vaccine outweighs its risk.
Programmatic pharmacovigilance process:
- • Case investigations of all severe, serious and non-serious AEFI, clusters and AEFIs of concern are conducted by the Department of Health.
- • Case investigation is done by a multi-disciplinary team from the district or the province preferably within 48 hours of reporting.
- • Once all the information about the case is available, Causality assessment is conducted by the National Immunisation Safety Expert Committee (NISEC).
- • NISEC is an independent ministerial advisory committee meeting on a weekly basis, and providing scientific advice and recommendations to the NDoH and SAHPRA.
- • Once causality assessments are completed, the NISEC assessments are shared with SAHPRA and the NDoH.
All severe, serious and non-serious cases will be assessed for causality by the NISEC.
- • An AEFI is considered a serious event if it
- o results in death;
- o is life-threatening;
- o requires inpatient hospitalisation or prolongs an existing hospitalisation;
- o results in persistent or significant disability/incapacity
- o causes a congenital anomaly/birth defect; or
- o is a medically significant event or reaction
- • Non-serious AEFIs usually resolve within a few days without any prolonged or persistent negative outcomes.
- • Events occurring above the expected rate or of unusual severity
- • Signals generated as a result of individual or clustered cases as these could signify a potential for large public health impact.
The selection of cases for Causality assessment focuses on:
- • Case investigation completed
- Case investigation completed, with both the Case Reporting and Case Investigation Forms.
- • Specific diagnosis
- There must be a specific ‘diagnosis’ (e.g. clinical sign, abnormal laboratory finding, symptom and/or disease) for the case, which is being investigated for a possible association with the vaccine.
- • Details and evidence
- All details of the case should be available at the time of assessment, including supporting documentation (e.g. clinical notes, laboratory results, post-mortem report).
Report the AEFI as soon as possible after identification, ideally within 24 hours. Provide as much details as possible about the case, including the following:
- • Details of the vaccine recipient (Name, Surname, ID number, contact details, home address, gender, province)
- • Name of the vaccine administered
- • AEFI experienced (provide as much detail as possible, what happened, when, how, etc.).
- • Co-existing medical conditions
- • Other medicines taken by the vaccine recipient (including traditional medicines)
- • Laboratory results
- • Post mortem investigation in the event of death occurring after vaccination
- A. Consistent with causal association to immunisation
- • Vaccine product-related reaction: Caused / precipitated by a vaccine due to one/more of the inherent properties of the vaccine product, even when the vaccine has been prepared, handled and administered correctly
- • Vaccine quality defect related: Caused / precipitated by a vaccine, due to one / more quality defects of the product, including its administration device, provided by manufacturer
- • Immunisation error-related reaction: Caused by inappropriate vaccine handling, prescribing or administration
- • Immunisation anxiety-related reaction: Arising from anxiety about the immunisation and fear of an injection
- B. Indeterminate
- • Temporal (Time) relationship is consistent but there is insufficient definitive evidence for vaccine causing event (may be new vaccine-linked event). Potential signal and maybe considered for investigation.
- • Qualifying factors result in conflicting trends of consistency and inconsistency with causal association to immunisation
- C. Inconsistent with causal association to immunisation
- • Coincidental event: An event that happens after vaccination but is not caused by the vaccine or vaccination process, because there are underlying or emerging condition(s), or a condition(s) caused by exposure to something other than vaccine.
- D. Unclassifiable
- • The case cannot be classified because the information available about the case is inadequate and additional information is required for classification.