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Serious adverse events (SAEs) in clinical trials require reporting within 24 hours, including a judgment of whether the SAE was related to the investigational product(s). Such assessments are an important component of pharmacovigilance, however classification systems for assigning relatedness vary across study protocols. This on-line survey evaluated the consistency of SAE causality assessment among professionals with vaccine clinical trial experience. METHODS: Members of the clinical advisory forum of experts (CAFÉ), a Brighton Collaboration online-forum, were emailed a survey containing SAEs from hypothetical vaccine trials which they were asked to classify. Participants were randomized to either two classification options (related/not related to study immunisation) or three options (possibly/probably/unrelated). The clinical scenarios, were i) leukaemia diagnosed 5 months post-immunisation with a live RSV vaccine, ii) juvenile idiopathic arthritis (JIA) 3 months post-immunisation with a group A streptococcal vaccine, iii) developmental delay diagnosed at age 10 months after infant capsular group B meningococcal vaccine, iv) developmental delay diagnosed at age 10 months after maternal immunisation with a group B streptococcal vaccine. RESULTS: There were 140 respondents (72 two options, 68 three options). Across all respondents, SAEs were considered related to study immunisation by 28% (leukaemia), 74% (JIA), 29% (developmental delay after infant immunisation) and 42% (developmental delay after maternal immunisation). Having only two options made respondents significantly less likely to classify the SAE as immunisation-related for two scenarios (JIA p=0.0075; and maternal immunisation p=0.045). Amongst study investigators (n=43) this phenomenon was observed for three of the four scenarios: (JIA p=0.0236; developmental delay following infant immunisation p=0.0266; and developmental delay after maternal immunisation p=0.0495). CONCLUSIONS: SAE causality assessment is inconsistent amongst study investigators and can be influenced by the classification systems available to them. There is a pressing need for SAE classification systems to be standardized across study protocols.


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