The IES-R is a 22-item measure commonly used to measure post-traumatic stress following a prespecified traumatic incident and has been used to evaluate the impact of infectious disease outbreaks on hospital staff.21 32 It contains eight items that focus on ‘intrusion’, eight items on ‘avoidance’ and six items on ‘hyperarousal’. The IES-R was used at the peak and deceleration survey phases. A score of 24 or above indicates a clinically significant traumatic stress response, a score above 33 indicates best cut-off for a diagnosis of ‘probable post-traumatic stress disorder’ (PTSD).33 34

The secondary outcomes captured included personal and professional characteristics and their association with psychological distress and trauma. These personal and professional factors were identified through rapid literature review of high-quality systematic reviews and meta-analysis by experts in pandemic research.1 21–23 All factors identified as predictors of outcome were retained. This was supplemented by factors deemed of specific or emerging interest by the expert study steering committee. These were defined a priori in the study protocol, with the exception of ethnicity which was added during the peak survey due to the specific emergence of ethnicity as a potential marker of poor physical health outcomes.24