Generating implementation evidence in clinical trials of vaccines and immunization-related technologies to reduce evidence-to-policy delays.

Evidence-to-policy delays pose a significant threat to the timely adoption of novel vaccine products despite their proven efficacy. Understanding the "how to" (i.e., implementation aspects) of innovative vaccine products can facilitate decision-making to fast-track prioritization and introduction. This perspective highlights the need to integrate implementation research within clinical trials of vaccines and immunization-related technologies to facilitate the generation of policy-relevant implementation evidence. We argue that implementation context, mechanisms, strategies, adaptation, and transportability should be systematically reported alongside efficacy outcomes to support decision-makers in informing policies regarding their use in routine settings. We propose a framework for embedding implementation research in vaccine development and advocate for stronger collaborations between research teams and policymakers. The success of implementation research within clinical trials of vaccine products depends on interdisciplinary expertise, proactive decision-maker engagement, and adherence to relevant implementation science reporting guidelines.