The disruption of clinical trials during the COVID-19 pandemic has been discussed widely, but no systemic study has quantitatively examined the multidimensional effect of COVID-19 on the clinical trials of non-COVID-19 diseases under a well-recognized disease classification system. By acquiring over 380,000 clinical trials from ClinicalTrials.gov and Dimensions, and automatically mapping trials with the WHO Global Health Estimates (GHE) cause category, this study explores the effect of COVID-19 on trials’ activeness, efficiency, and international collaboration. Beyond the global perspective, a granular comparative analysis using the United States, China, Japan, and the United Kingdom as representative cases is conducted. Utilizing an interrupted time series model, we find that while the aggregate number of trial registrations has remained relatively stable, there is a notable crowding-out effect for non-COVID-19 diseases, affecting both noncommunicable and communicable diseases. Interestingly, despite heightened focus on COVID-19 research, trial efficiency for other diseases remained largely unaffected. COVID-19 prompted increased global collaboration in clinical research. Through further categorization of sponsorship type and identification of digitized trials by text-mining analysis, we summarize and validate three potential factors to shed light on the observed effects of COVID-19 on clinical studies. Additionally, valuable insights and essential lessons in managing unprecedented pandemics are discussed.

John Desmond Bernal (1901–1970) was one of the most eminent scientists in molecular biology and is also regarded as the founding father of the science of science. His book The social function of science laid the theoretical foundations for the discipline. In this article, we summarize four chief characteristics of his ideas in the science of science: the sociohistorical perspective, theoretical models, qualitative and quantitative approaches, and studies of science planning and policy. China has constantly reformed its scientific and technological system based on research evidence of the science of science. Therefore, we analyze the impact of Bernal’s science-of-science thoughts on the development of China’s science of science, and discuss how they might be usefully taken still further in quantitative studies of science.