ABSTRACT
Background: Coronavirus disease 2019 (COVID-19) has generated an unprecedented clinical research response, but the data about the characteristics of COVID-19-related clinical studies were scarce. The study aimed to describe the characteristics of COVID-19-related clinical studies registered at ClinicalTrials.gov and further identify factors affecting the recruitment and completeness of these studies. Methods: : The study extracted 5,672 studies and included 5,430 studies relating to COVID-19 registered at ClinicalTrials.gov. We presented the characteristics of all included clinical studies. Identification of risk factors for recruitment status was achieved using the multiple logistic regression models, and identification of risk factors for completion time was obtained using the multiple Cox proportional hazards regression models. Subgroup analyses were also performed in the interventional studies. Results: : Of the included studies, only 19.59% (1064/5430) had completed recruitment, and 55.93% (3037/5430) were interventional studies. The peak of the number of clinical studies relating to COVID-19 was seven months earlier than the first peak of the number of COVID-19 cases globally. In all included studies, participants only including male (P=0.02), Participants including child (P=0.01), smaller enrollment (P<0.01), and studies not being funded by industry (P=0.01) and the National Institutes of Health (NIH) (P<0.01), and observational studies (P<0.01) tended to be associated to higher completed recruitment rates. Regarding the interventional studies, Participants including child (P=0.04), smaller enrollment (P<0.01), a crossover intervention model (P<0.01), and primary purpose involving in device feasibility (P<0.01) and treatment (P=0.03) were associated with shorter completion time, while being funded by industry (P=0.01) and NIH (P<0.01), primary purpose involving in basic science (P<0.01), and biological interventions (P<0.01) were associated with longer completion time. Conclusion: A multitude of clinical studies relating to COVID-19 are registered in responding to the pandemic and the response is rapid and timely, but these clinical studies are frequently not completed. Increased focus on establishing global initiatives and networks to coordinate recruitment efforts may be needed. Several independent risk factors are identified to guide the design of COVID-19-related clinical studies. This may be significant to avoid waste and ensure that the participation of all participants in clinical researches contributes to the treatment or prevention of COVID-19.