The primary challenge for patient recruitment is that of awareness. With the majority of people being simply unaware of the existence of clinical trials they could participate in.
While the Covid pandemic did go some way to increasing awareness about trials, there remains a significant lack of knowledge regarding trials for non-Covid conditions. So while people knew there were trials for Covid vaccines, they didn’t necessarily relate that to the idea that there might be trials for other conditions.
Another notable issue is that healthcare professionals, who you would think would be ideally placed for introducing trials to patients, often themselves lack awareness of relevant trials. And their limited inclination to explore trials is further constrained by the time pressures of patient appointments.
Also, patients typically do not actively seek out trials for themselves. Such that the industry relies quite heavily on targeted messaging, such as through digital advertising, to reach potential trial volunteers.