Introduction: Maternal vaccination and infant monoclonal antibodies are promising avenues to protect young infants from respiratory syncytial virus (RSV) infection. Successful inclusion into the UK immunisation schedule depends on parental acceptability, among other factors. Methods: An online cross-sectional survey from August to September 2023 exploring the likelihood of accepting, and preference for, either method of RSV prophylaxis, and reasons given for these. A questionnaire was distributed via social media networks to UK participants with a child under the age of 2 years and/or pregnant. Results: A total of 1620 participants completed the survey. Participants median age was 33 years (IQR 31 -36), 92% were of White ethnicity. Acceptability was high, but higher for a maternal vaccine than an infant monoclonal antibody (p<0.0001). Concerns about safety, need for more information, and number of vaccines given to infants already were common reasons for hesitancy. Lacking knowledge about RSV was associated with a lower likelihood of accepting either option (maternal vaccine: OR 0.32, 95% CI 0.16-0.68, p=0.002; infant monoclonal antibody: OR 0.35, 95% CI 0.19-0.68, p= 0.002), as was identifying as Black, Black British, African or Caribbean ethnic group, or having declined the routinely recommended antenatal vaccines. Conclusions: Whilst most parents would accept a maternal vaccine or infant monoclonal antibody to protect their infant against RSV, understanding preferences, influencing factors and concerns is essential to optimise immunisation programmes. This study highlights the information parents require to make an informed choice about RSV protection.

CEJ is a member of the executive board of the IMPRINT Network. She is national coordinating investigator for a clinical trial of an investigational RSV vaccine on behalf of University Hospital Southampton, sponsored by Moderna, but has received no personal funding. She attended an advisory board for Sanofi where RSV prevention strategies were discussed and received personal funding for this. She is a member of the JCVI RSV subcommittee. SP and APSM are sub-investigators for the HARMONIE clinical trial of nirsevimab, sponsored by Sanofi, but receive no personal funding. KC acts on behalf of University Hospital Southampton NHS Foundation Trust as an investigator and/or providing consultative advice on studies funded or sponsored by vaccine manufacturers including AstraZeneca, GlaxoSmithKline, Janssen, Medimmune, Merck, Pfizer, Sanofi, Iliad and Valneva. She receives no personal financial payment for this work.

This research was funded by IMPRINT (Immunising Pregnant Women and Infants Network, funded by the GCRF Networks in Vaccines Research and Development, which was co-funded by the Medical Research Council (MRC) and the Biotechnology and Biological Sciences Research Council (BBSRC). It is part of the EDCTP2 programme, supported by the European Union.

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The study was conducted in accordance with the Declaration of Helsinki, and approved by the Faculty of Medicine Ethics Committee, University of Southampton (ERGO number 82762, 14th August 2023).

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