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

From: The COVID-19 pandemic and new clinical trial activations

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
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
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
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
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
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
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
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
Non-US   119.0 (n = 476) 112.5 1.06 0.95, 1.18 .32    
  1. 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