Retention of participants recruited to a multi-year longitudinal study via Prolific

Despite increasing use of the crowdsourcing platform Prolific in psychological research, there is limited data on the retention of participants in longitudinal studies using this recruitment channel. We present a summary of retention within a study on vaccination attitudes with three time points conducted via Prolific. Of the 331 participants who completed the initial survey in 2018, 254 (76.74% of total Time 1 sample; 96.95% of active users) completed the Time 2 survey approximately 12 months later, and 205 (61.93% of total Time 1 sample) completed the Time 3 survey at 19 months. At both Time 2 and Time 3 the majority of participants completed the follow-up survey within 24 hours of survey launch. Older participants were more likely to be retained. However, retention was not related to gender, educational attainment, health related belief or behaviour, speed of survey completion, or time to recruitment at Time 1. Overall, Prolific shows similar retention characteristics to conventional cohort studies with substantially reduced researcher burden.