The COVID-19 pandemic and new clinical trial activations

Table 1 Comparison of estimated relative change in monthly number of trials in US and non-US regions

Initial pandemic period
		Monthly trial registrations¹			Relative risk (RR)¹			RR ratio (US versus non-US)²
Trial type	Region	Fitted value (n) 2015–Jan 2020	Fitted value (n) Feb–May 2020	Expected value³ Feb–May 2020	RR	95% CI	p value	Risk ratio	95% CI	p value
All trials	US	320.1 (n = 19,524)	201.5 (n = 806)	355.6	0.57	0.52, 0.61	< .001	0.73	0.67, 0.81	< .001
All trials	Non-US	539.0 (n = 32,876)	437.0 (n = 1748)	565.9	0.77	0.73 0.82	< .001
Oncology	US	180.8 (n = 11,028)	120.5 (n = 482)	196.7	0.61	0.55, 0.68	< .001	0.76	0.67, 0.87	< .001
Oncology	Non-US	267.9 (n = 16, 344)	234.0 (n = 936)	290.9	0.80	0.75, 0.87	< .001
Cardiovascular	US	75.6 (n = 4, 609)	44.0 (n = 176)	80.6	0.55	0.46, 0.65	< .001	0.75	0.61, 0.90	.003
Cardiovascular	Non-US	189.5 (n = 11, 558)	135.3 (n = 541)	184.6	0.73	0.66, 0.81	< .001
Mental health	US	77.3 (n = 4, 713)	46.6 (n = 186)	93.8	0.50	0.42, 0.58	< .001	0.69	0.56, 0.84	< .001
Mental health	Non-US	97.6 (n = 5, 955)	81.3 (n = 325)	112.3	0.72	0.64, 0.82	< .001
Reopening period
			Fitted value (n) Jun–Sep 2020	Expected value³ Jun–Sep 2020
All trials	US		338.5 (n = 1, 354)	351.7	0.96	0.90, 1.03	.25	0.87	0.80, 0.95	< .001
All trials	Non-US		645.0 (n = 2580)	584.8	1.1	1.05, 1.16	< .001
Oncology	US		201.8 (n = 807)	189.4	1.06	0.98, 1.16	.15	0.93	0.83, 1.03	.18
Oncology	Non-US		345.8 (n = 1, 383)	301.3	1.14	1.07, 1.23	< .001
Cardiovascular	US		73.3 (n = 293)	80.2	0.91	0.80, 1.05	.20	0.88	0.75, 1.03	.11
Cardiovascular	Non-US		202.0 (n = 808)	193.9	1.04	0.96, 1.13	.35
Mental health	US		78.3 (n = 313)	94.7	0.83	0.72, 0.94	.005	0.78	0.66, 0.78	.005
Mental health	Non-US		119.0 (n = 476)	112.5	1.06	0.95, 1.18	.32

¹Total counts for each disease exceed the disease-specific counts noted in the text due to the inclusion of multiple disease studies. ²Derived from Poisson regression model, adjusting for calendar month using indicator variables, including interaction terms to derive the risk ratios. ³Expected (or counterfactual) monthly average number of trial registrations in the absence of the COVID-19 pandemic. Model expected results based on Poisson regression, adjusting for calendar month using indicator variables

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