Childhood Vaccination Communication Outcomes Unpacked and Organized in a Taxonomy to Facilitate Core Outcome Establishment

"Given the variety of vaccination communication strategies, it follows that there should be a similarly wide range of potential outcomes, from socially oriented outcomes related to communication and engagement to health status and health service outcomes, such as vaccination status or timely delivery....But many of these relevant outcomes are not being adequately assessed."

This article shares a taxonomy that is an exploration of the potential outcomes associated with vaccination communication, bringing to light a range of concepts that might help to unpack how these complex communication interventions are - or are not - working. Emerging from the Communicate to Vaccinate (COMMVAC) project's three-stage study into the outcomes of vaccination communication, this taxonomy is a tool for trialists or programme evaluators as they select the outcomes to report for a vaccination communication evaluation or by intervention designers and theorists hypothesising and testing communication strategies for behaviour change.

As the researchers explain, the term 'vaccination communication' includes many interventions with a number of aims or purposes: to inform or educate, remind or recall, enhance community ownership, teach skills, provide support, facilitate decision-making, and enable communication. It is often delivered in complex packages with multiple components. Because current evidence for vaccination communication focuses on a few end points, without measuring process outcomes, it is often not clear why an intervention did or did not influence vaccination outcomes. To better understand the impacts of vaccination communication interventions, the researchers indicate that we need to measure similar outcomes consistently across studies, and these outcomes need to reflect the intervention's theorised mechanism of action. This requires a conceptual understanding and identification of the full range of potentially relevant effects that may be outcomes of vaccination communication. It is also important to consider that different outcomes may be important to different stakeholders.

The researchers combined several methods to develop the outcome taxonomy. The outcomes are derived not only from existing trials and stakeholder consultation, but also through identifying and translating outcomes from the broader health communication area. The researchers also conducted parent and health care professional focus groups. They organised outcomes into the taxonomy through iterative discussion and informed by organisational principles established by leaders in core outcome research.

The taxonomy includes three overarching core areas, divided into eight domains and then into outcomes. Core area one is psychosocial impact (see Table 3 on page 180), including the domains "knowledge or understanding," "attitudes or beliefs," and "decision-making." Core area two (see Table 4 on page 180) is health impact, covering "vaccination status and behaviors" and "health status and well-being." Core area three (see Table 5 on page 181) is community, social, or health system impact, containing "intervention design and implementation," "community participation," and "resource use."

Among the issues explored in the discussion section is the potential value of the taxonomy development methods and format to core outcome set (COS) researchers in other fields, particularly those interested in complex or communication-related interventions. The researchers also discuss the importance of intermediate outcomes, reiterating that communication is a complex, often multifaceted intervention whose effects cannot be unpacked with trials measuring outcomes dominated by "hard" end points. "Moving into the future, we need to focus on the right outcomes to ensure that evaluations produce meaningful evidence that advances the field and contributes to improved interventions."

By using the taxonomy to prioritise key outcome domains in the Delphi consultation that followed this stage of the COMMVAC project, the researchers hoped to bring methodological research attention to those outcomes that are considered important but for which no validated instrument yet exists.