Table 4.

Selection of appropriate numerators and denominators from a Venn diagram based on SwissCovid digital proximity tracing app use after respondent follow-up. Letters in square brackets—[]—reflect subpopulations (Venn segments) of app users and those in curly brackets—{}— reflect the subset of individuals who did not use the app.

Indicator			Numerator		Denominator		% (95% CI)
Coverage of app users
	All	[C,D,E1,E2,F1,F2,G1,G2,N,T]		C,D,E1,E2,F1,F2,G1,G2,N,T		49.15 (47.13-51.17)
	Tested	[C,D,E1,F1,G1,T]		C,D,E1,F1,G1,T		57.14 (52.66-61.54)
	Tested positive	[C,D]		C,D		58.70 (43.23-73.00)
	Quarantined	[C,D,F1,F2,G1,G2]		C,D,F1,F2,G1,G2		54.62 (45.65-63.36)
Individuals tested
	Nonuser	{D,G1,T}		{D,G1,G2,N,T}		17.43 (15.34-19.68)
	App user	[D,G1,T]		[D,G1,G2,N,T]		22.92 (20.52-25.45)
	App user and received exposure notifications	[C,E1,F1]		[C,E1,E2,F1,F2]		68.97 (49.17-84.72)
Test positivity
	Nonuser	{D}		{D,G1,T}		8.92 (5.46-13.58)
	App user	[D]		[D,G1,T]		7.95 (4.99-11.90)
	App user and received exposure notifications	[C]		[C,E1,F1]		30.00 (11.89-54.28)
Quarantined
	Nonuser	{D,G1,G2}		{D,G1,G2,N,T}		4.83 (3.70-6.18)
	App user	[D,G1,G2]		[D,G1,G2,N,T]		4.95 (3.77-6.36)
	App user and received exposure notifications	[C,F1,F2]		[C,E1,E2,F1,F2]		48.28 (29.45-67.47)
Quarantine (among those tested)
	Nonuser	{D,G1}		{D,G1,T}		19.72 (14.60-25.70)
	App user	[D,G1]		[D,G1,T]		16.67 (12.38-21.72)
	App user and received exposure notifications	[C,F1]		[C,E1,F1]		65.00 (40.78-84.61)
App users who received an exposure notification who later tested positive			[C]		[C,D]		22.22 (8.62-42.26)
App users who received an exposure notification who later tested negative			[E1,F1]		[E1,F1, G1,T]		5.45 (3.01-8.97)