The US National Institutes of Health (NIH) has registered trials in 172 countries on its clinicaltrials.gov website and this information is displayed in two maps below.
Various sources give different numbers of countries in the world, for instance the United Nations has 192 members and the US state department recognises 194 independent states, but whichever figure is taken it is clear the NIH list covers most of the world.
Notable gaps in terms of land mass, excluding the US which is dealt with separately, include Turkmenistan, Chad and Namibia. There are three trials in the Democratic Republic of Congo but these are not displayed on the map.
The US map is equally complete, with trials ongoing in all states and the District of Columbia. High numbers of trials are taking place in California, Texas and New York. Wyoming has the fewest trials occurring, with 218 currently in progress in the state.
Answering the initial questions, Illinois’ 6854 trials top Italy’s 2955 and Mongolia’s two studies put it just ahead of Macau, which currently has one ongoing.
Data was collected from the clinicaltrials.gov website on the week commencing 24th August. Figures may have changed since the data was collected.