Normalising enhanced influenza vaccines as a strategy to promote vaccination uptake in healthcare workers: Insights from a discrete choice experiment

BACKGROUND: Advancements in enhanced influenza vaccines have presented opportunities for better infection control but pose unknown impacts on vaccination uptake. By eliciting vaccine preferences among practising nurses, this study projected the impact on vaccination coverage following the rollout of different influenza vaccines in Hong Kong. METHODS: In March 2025, practising nurses were invited to participate in a discrete choice experiment. Based on their vaccine selection pattern in 48 choice situations, the relative importance of six vaccine attributes (effectiveness, probability of adverse reaction, protective duration, mode of administration, concomitant COVID-19 protection, and age of vaccine technology) was determined using random parameter logit model. Using the attributes to emulate different influenza vaccines, their uptake was modelled assuming free distribution at workplace. Interaction effects were evaluated to reveal preference heterogeneity. RESULTS: Of 726 respondents analysed (87% female; median age 39 years), 62% were vaccinated against influenza in the 2024/25 season. With 13% selecting "opt-out" in all situations, novel vaccine technology (approved for ≤2 years) and increased adverse reactions (10% more) were inferred to deter vaccination, resembling a 26% and 19% reduction in vaccine effectiveness, respectively. A six-month longer protection, intranasal administration and concurrent COVID-19 protection were found to motivate uptakes, mirroring a 16%, 16% and 11% increase in effectiveness. Through simulations, switching from the conventional inactivated influenza vaccine (IIV) to recombinant influenza vaccine was projected to expand the coverage by 13%. Deploying intranasal vaccines is anticipated to boost uptakes in nurses aged 18-49 years by 14%. In those aged ≥50 years, the supply of adjuvanted and high-dose IIV was predicted to reduce vaccination rates by 10.5% and 17.5%, respectively. Older nurses preferred vaccines with extended protection, while those less adhered to annual vaccination favoured intranasal vaccines. CONCLUSIONS: Enhanced influenza vaccines should be normalised in workplace campaigns targeting healthcare workers for promoting vaccine acceptance.