Factors that influence recruitment to COVID-19 vaccine trials: a qualitative evidence synthesis

The COVID-19 pandemic marked a unique period characterised by an extraordinary global virus spread. The collective effort to halt the transmission of the virus led to various public health initiatives, including a variety of COVID-19 vaccine trials. Many of these trials used adaptive methods to address the pandemic's challenges, such as the need for rapid recruitment. These adaptive methods allow for modifications to the trial procedures without undermining the trial's integrity, making the research process more flexible and efficient. However, recruiting participants for vaccine trials remains a considerable challenge. The aim of this qualitative evidence synthesis (QES) is to explore the factors that influence a person's decision to participate in a COVID-19 vaccine trial. Lessons learned from this could help shape future trials' design and conduct, particularly those conducted within a pandemic.

We conducted a systematic search for qualitative studies and mixed methods studies with a qualitative component in the WHO COVID-19 Research Database, MEDLINE, CINAHL, PsycINFO, Epistemomikos, Online Resource for Research in Clinical Trials (ORCCA), and the Cochrane COVID-19 Study Register. We used the best-fit framework synthesis approach and the Social Ecological Model as an a priori framework. We used the GRADE-CERQual approach to assess our confidence in the review findings.

Five studies involving 539 participants were included. One of these studies included participants in a COVID-19 vaccine trial. In three of the studies, participants were asked hypothetically about their attitudes. Another study included people who had either not responded to or declined an invitation to participate in a COVID-19 vaccine trial. We developed six themes outlining the factors that influence a person's decision to participate in a COVID-19 vaccine trial: (1) personal gains, (2) perceived risk, (3) influence of family and community, (4) contributing for others, (5) institutional trust and mistrust, and (6) accessibility of the trial.

This review sheds light on how people perceive the potential personal, family, and community advantages of trial participation and how these perceptions may be weighed against concerns about vaccine safety. The findings also point toward specific aspects of trial methodology to consider when designing COVID-19 vaccine trials.