Background Web-based respondent-driven sampling is a novel sampling method for the recruitment of participants for generating population estimates, studying social network characteristics, and delivering health interventions. However, the application, barriers and facilitators, and recruitment performance of web-based respondent-driven sampling have not yet been systematically investigated. Objective Our objectives were to provide an overview of published research using web-based respondent-driven sampling and to investigate factors related to the recruitment performance of web-based respondent-driven sampling. Methods We conducted a scoping review on web-based respondent-driven sampling studies published between 2000 and 2019. We used the process evaluation of complex interventions framework to gain insights into how web-based respondent-driven sampling was implemented, what mechanisms of impact drove recruitment, what the role of context was in the study, and how these components together influenced the recruitment performance of web-based respondent-driven sampling. Results We included 18 studies from 8 countries (high- and low-middle income countries), in which web-based respondent-driven sampling was used for making population estimates (n=12), studying social network characteristics (n=3), and delivering health-related interventions (n=3). Studies used web-based respondent-driven sampling to recruit between 19 and 3448 participants from a variety of target populations. Studies differed greatly in the number of seeds recruited, the proportion of successfully recruiting participants, the number of recruitment waves, the type of incentives offered to participants, and the duration of data collection. Studies that recruited relatively more seeds, through online platforms, and with less rigorous selection procedures reported relatively low percentages of successfully recruiting seeds. Studies that did not offer at least one guaranteed material incentive reported relatively fewer waves and lower percentages of successfully recruiting participants. The time of data collection was shortest in studies with university students. Conclusions Web-based respondent-driven sampling can be successfully applied to recruit individuals for making population estimates, studying social network characteristics, and delivering health interventions. In general, seed and peer recruitment may be enhanced by rigorously selecting and motivating seeds, offering at least one guaranteed material incentive, and facilitating adequate recruitment options regarding the target population’s online connectedness and communication behavior. Potential trade-offs should be taken into account when implementing web-based respondent-driven sampling, such as having less opportunities to implement rigorous seed selection procedures when recruiting many seeds, as well as issues around online rather than physical participati...

Background Online respondent-driven detection (RDD) is a novel method of case finding that can enhance contact tracing (CT). However, the advantages and challenges of RDD for CT have not yet been investigated from the perspective of public health professionals (PHPs). Therefore, it remains unclear if, and under what circumstances, PHPs are willing to apply RDD for CT. Methods Between March and April 2019, we conducted semi-structured interviews with Dutch PHPs responsible for CT in practice. Questions were derived from the ‘diffusion of innovations’ theory. Between May and June 2019, we distributed an online questionnaire among 260 Dutch PHPs to quantify the main qualitative findings. Using different hypothetical scenarios, we assessed anticipated advantages and challenges of RDD, and PHPs’ intention to apply RDD for CT. Results Twelve interviews were held, and 70 PHPs completed the online questionnaire. A majority of questionnaire respondents (71%) had a positive intention towards using RDD for CT. Anticipated advantages of RDD were ‘accommodating easy and autonomous participation in CT of index cases and contact persons’, and ‘reaching contact persons more efficiently’. Anticipated challenges were ‘limited opportunities for PHPs to support, motivate, and coordinate the execution of CT’, ‘not being able to adequately convey measures to index cases and contact persons’, and ‘anticipated unrest among index cases and contact persons’. Circumstances under which PHPs anticipated RDD applicable for CT included index cases and contact persons being reluctant to share information directly with PHPs, digitally skilled and literate persons being involved, and large scale CT. Circumstances under which PHPs anticipated RDD less applicable for CT included severe consequences of missing information or contact persons for individual or public health, involvement of complex or impactful measures for index cases and contact persons, and a disease being perceived as severe or sensitive by index cases and their contact persons. Conclusions PHPs generally perceived RDD as a potentially beneficial method for public health practice, that may help overcome challenges present in traditional CT, and could be used during outbreaks of infectious diseases that spread via close contact. The circumstances under which CT is performed, appear to strongly influence PHPs’ intention to use RDD for CT.

Background: Online respondent-driven detection (online-RDD) is a novel method of case-finding that can enhance contact tracing. However, the advantages and challenges of online-RDD for contact tracing (CT) have not yet been investigated from the perspective of public health professionals (PHPs). Therefore, it remains unclear if, and under what circumstances, PHPs are willing to apply online-RDD for contact tracing. Methods: First, between March and April 2019, we conducted semi-structured interviews with Dutch PHPs responsible for CT in practice. Questions were derived from the diffusion of innovations theory. Second, between May and June 2019 we distributed an online questionnaire to 260 Dutch PHPs to quantify the main qualitative findings. Using hypothetical scenarios that involved close-contact pathogens (scabies, shigella, and mumps), we assessed anticipated advantages and challenges of online-RDD and PHPs intention to apply online-RDD for contact tracing. Results: Twelve interviews were held and 70 PHPs filled in the online questionnaire. A majority of questionnaire respondents (71%) had a positive intention towards using online-RDD for contact tracing. Anticipated advantages of online-RDD were related to accommodating easy and autonomous participation in contact tracing of patients and contact persons, and reaching contact persons more efficiently. Anticipated challenges with online-RDD were related to limited opportunities for PHPs to support, motivate, and coordinate the execution of contact tracing, adequately conveying measures to patients and contact persons, and anticipated unrest among patients and contact persons. Online-RDD was considered more applicable when patients and their contact persons are reluctant to share sensitive information directly with PHPs, digitally skilled and literate persons are involved, and the scope of contact tracing is large. Online-RDD was considered less applicable when consequences of missing information or individuals are severe for individuals - or public health, when measures that patients and contact persons need to undertake are complex or impactful, and when a disease is perceived as particularly severe or sensitive by patients and their contact persons. Conclusions: PHPs generally perceived online-RDD as beneficial to public health practice. The method can help overcome challenges present in regular CT and could be used during outbreaks of infectious diseases that spread via close-contact, such as the SARS-CoV-2 virus. We propose a staggered implementation study to further investigate the application of online-RDD for enhanced CT during the ongoing COVID-19 pandemic.