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Over 1,200 clinical trials worldwide have ground to a halt due to COVID-19

Over 1,200 clinical trials worldwide have ground to a halt due to the impact of the COVID-19 pandemic, a new analysis of data on the American trial registry shows. Overall, the number of trials that are being terminated, suspended or withdrawn has more than doubled since the onset of the pandemic.

The data confirms widespread fears that even as new COVID-19 trials are being launched at a dizzying pace, clinical research into other conditions is taking a massive hit.

Between the beginning of December 2019 and this week, 2,522 clinical trials have been terminated, suspended or withdrawn. Of those, 1,099 trials explicitly cite COVID-19 as the reason for discontinuation.

A total of 39,405 patients were enrolled in trials stopped due to COVID-19 that provide actual enrollment figures on the registry. Together, the trials that were stopped due to Covid-19 were testing 538 unique drugs or biologicals.

A comparison with 2017-2018 figures for the same months shows a 105% increase in trial discontinuations, suggesting that the true number of trials affected by the pandemic exceeds 1,200. (Note: This figure is likely an underestimate, as the data only includes trials listed on one trial registry,

As the chart below shows, there was a spike in the number of trials being terminated, suspended or withdrawn from mid March 2020 onwards.

Note: The data above includes interventional clinical trials listed on that were terminated, suspended or withdrawn between 01 December 2019 and 05 May 2020, including trials conducted outside the United States. It does not include data from other trial registries.

The widespread discontinuation of trials due to Covid-19 is causing setbacks for entire programmes of human research.

It is likely to delay the advent of new drugs, the gathering of evidence on drugs’ efficacy in new indications or combinations, and the generation of informative negative results.

Besides affecting industry, academic research institutions and the individuals involved in running clinical trials, these disruptions to medical research also directly impact patients who were enrolled in these clinical trials, as they may not receive the treatment they had anticipated. Further, patient expectations regarding their contribution to new medical knowledge may also not be met.

While some of these trials have probably been suspended with the intention of resuming at a later point in time, restarting them may sometimes not be feasible.

Even trials that do resume may have to contend with financial difficulties, reduced statistical power, or the need to change protocols or statistical analysis plans. Some trials will have to recruit additional patients to make up for data lost or rendered unusable by the interruption.

Meanwhile, clinical trials that were terminated early – before they reached their target enrolment figure – may be unable to answer the questions they originally set out to answer.

In addition to the general disruptions to life wrought by the pandemic, recent regulatory guidance by the FDA and the EMA that aims to safeguard the well-being of trial participants and curb the further spread of COVID-19 is likely to be a factor driving trial discontinuations.

The figures cited above are from an online ‘living paper’ that quantifies the number of clinical trials that have been terminated, suspended or withdrawn due to Covid-19, and that explores the impact on different stakeholders in clinical research. The data set and analyses are automatically updated every day based on registry data. Clinical trials that cite COVID-19 as the reason for discontinuation are identified manually. The set of clinical trials that stopped during the same time period two years earlier acts as a baseline.

The ‘living paper’ will continue to extract and analyse data on trial discontinuations, reasons stated for discontinuation, and patient enrollment figures on an ongoing basis in order to document the impact of the pandemic on trialists, patients, and medical research.

The draft report, figures and data are available at The protocol has been registered with the Open Science Foundation, and the source code for the web app that produced and updates the data set is on Codeberg.

This guest blog was written by Benjamin Gregory Carlisle, a Research Fellow at the BIH QUEST Center in Berlin, where his work revolves around research ethics, medical ethics, bioethics, and artificial intelligence in human research (publications here). His previously built the Clinical Trials Viewer, an online tool that uses registry data to visualise drug development pipelines. The content of this guest blog is his alone; TranspariMED did not verify the data cited.

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