Assessing the relationships between capability, opportunity, and motivation in influencing self-isolation behaviour during pandemics.

Adherence to self-isolation was a central measure for controlling the spread of COVID-19; however, compliance varied widely. Understanding the behavioural determinants that drive adherence is critical for informing future public health intervention. This study applied the COM-B model to examine the associations between capability, opportunity, motivation, and self-isolation behaviour during the COVID-19 pandemic in the United Kingdom. A retrospective analysis was conducted using secondary data from the UK Office for National Statistics 2019 Opinions and Lifestyle Survey, which was not originally designed to measure COM-B constructs. Structural equation modelling (SEM) was used to examine the relationships between capability, opportunity, motivation, and self-isolation behaviour. Opportunity and motivation were significantly associated with self-isolation, while capability was linked to behaviour indirectly through its association with motivation, reflecting a possible pathway suggested by the structural model. Although some measurement indicators demonstrated lower reliability owing to the use of secondary data, the overall model fit was good (RMSEA = 0.049, CFI = 0.966, TLI = 0.944, SRMR = 0.040). These findings highlight the dominant influence of social and motivational factors in shaping adherence. This study demonstrates the utility of the COM-B model for understanding self-isolation behaviour despite the constraints of secondary data. The findings highlight opportunity and motivation as key levers for promoting adherence and offer actionable insights for policymakers to design interventions that enhance motivation, strengthen social support, and sustain compliance during future public health emergencies.