Table 1.

SPIDER framework

Sample	Adults (age > 18) who have been invited to participate in a COVID-19 vaccine trail and adults who have not received an invitation but who were asked about their attitudes towards participating
Phenomenon of interest	Factors that influence recruitment to COVID-19 vaccine trials
Design	Primary qualitative studies (e.g. ethnography, phenomenology, case studies, grounded theory studies) that use recognised methods of qualitative data collection (e.g. focus groups, interviews, observations) and analysis (e.g. thematic analysis, framework analysis). Mixed-methods studies, if data were collected and analysed using qualitative methods, and qualitative data can be extracted
Evaluation	The synthesis focused on people’s attitudes, motivations, barriers to participating in a COVID-19 vaccine trial
Research type	Qualitative or mixed methods