Table 2.

Table of patients meeting the EU ARI and the EU ILI case definitions among study sites using the EU ARI case definition to recruit patients (n = 31 645), study on effect of case definition on influenza vaccine effectiveness, VEBIS primary care multicentre case-control study, EU/EEA, 2022–23.

		Meets ILI case definition
	Meets ARI case definition	No	Yes	Missingb	Total
All	No	2 031	0	0	2031
	Yes	2 564	24 243	470	27 277
	Missinga	23	0	2 314	2337
	Total	4 618	24 243	2 784	31 645
Influenza cases	No	439	0	0	439
	Yes	160	6 524	31	6715
	Missinga	0	0	479	479
	Total	599	6 524	510	7633
Controls	No	1 592	0	0	1592
	Yes	2 404	17 719	439	20 562
	Missinga	23	0	1 835	1858
	Total	4 019	17 719	2 274	24 012

^aThe ARI case definition was coded as “missing” among patients with missing information for “sudden onset” or where at least one of the four respiratory symptoms was coded as missing and none was coded as “yes”.

^bThe ILI case definition was coded as “missing” among patients with missing information for “sudden onset” or where at least one of the four systemic symptoms was coded as missing and none was coded as “yes” or where at least one of the three respiratory symptoms (cough, sore throat, shortness of breath) was coded as missing and none was coded “yes”.