Understanding parental decisions to decline or delay infant RSV immunisation, nirsevimab, in Western Australia in 2024

Purpose: In 2024, the government of Western Australia introduced ‘nirsevimab’, a monoclonal antibody offering protection from respiratory syncytial virus (RSV), for eligible infants. This study explores why parents of infants who were eligible to receive nirsevimab opted to decline or delay the immunisation. Methods: Semi-structured, qualitative interviews were conducted with eleven parents to understand rationales for their decline or delay decision, their knowledge and understanding of RSV infection, and their broader attitudes to immunisation. Interview responses were inductively and deductively coded and analysed. Findings and conclusion: Factors shaping parents' decline or delay decisions included concerns as to the safety and potential side effects of nirsevimab, lack of knowledge or under-estimation of disease risk and burden of RSV, reasoning based on alternative risk mitigation strategies and conditions, and following healthcare provider advice. This study is one of few globally, and the first if its kind in Australia, to use qualitative methods to deeply explore parental decline or delay of infant RSV immunisation. Its significant contribution to knowledge can aid strategic improvements in rollout and maintenance of infant RSV immunisation programs in Australia and globally.