Abstract
Background
The quality of evidence about the effectiveness of non-pharmaceutical
health interventions is often low, but little is known about the effects of
communicating indications of evidence quality to the public.
Methods
In two blinded, randomised, controlled, online experiments, US
participants (total n=2140) were shown one of several versions of an
infographic illustrating the effectiveness of eye protection in reducing
COVID-19 transmission. Their trust in the information, understanding,
feelings of effectiveness of eye protection, and the likelihood of them
adopting it were measured.
Findings
Compared to those given no quality cues, participants who were told the
quality of the evidence on eye protection was ‘low’, rated the evidence less
trustworthy (p=.001), and rated it as subjectively less effective (p=.020).
The same effects emerged compared to those who were told the quality of the
evidence was ‘high’, and in one of the two studies, those shown ‘low’
quality of evidence said they were less likely to use eye protection
(p=.005). Participants who were told the quality of the evidence was ‘high’
showed no significant differences on these measures compared to those given
no information about evidence quality.
Interpretation
Without quality of evidence cues, participants responded to the evidence
about the public health intervention as if it was high quality and this
affected their subjective perceptions of its efficacy and trust in the
provided information. This raises the ethical dilemma of weighing the
importance of transparently stating when the evidence base is actually low
quality against evidence that providing such information can decrease trust,
perception of intervention efficacy, and likelihood of adopting it.
Funding
The Winton Centre for Risk & Evidence Communication, thanks to the
David & Claudia Harding Foundation
Research in Context
Evidence before this study
This is the first quantitative, empirical study, to our
knowledge, on the effects of communicating the quality of
evidence underlying an effectiveness estimate of a public health
intervention on a public audience.
Added value of this study
This study provides novel insights into the effects of
quality of evidence communication in a public health context. It
is thus of high theoretical as well as translational
value.
Implications of all the available evidence
Members of the public may assume that information around the
effectiveness of a measure such as wearing eye protection to
protect against COVID-19 are based on high quality evidence if
they are given no cues to suggest otherwise. Yet, when given a
statement of the quality of the evidence, this can
(appropriately) affect their feelings of the trustworthiness of
the information and their subjective judgement of the
effectiveness of the measure. This raises the issue of whether
there is an ethical imperative to communicate the quality of
underlying evidence, particularly when it is low, albeit with
the recognition that this may reduce uptake of a public health
measure.
The Public Health Intervention for International Students at Universiti Malaysia Sabah, Malaysia
