Table 2. Number of individuals with symptomatic SARS-CoV-2 infections included in the proportional hazard regression for analysis of vaccine effectiveness against hospitalisation, Belgium, 12 July 2021–26 May 2022 (n = 734,115).

Variant of concern	Age group (years)	Sex	Unvaccinated		Primary vaccination		Booster vaccination
			n	Proportion in CHS	n	Proportion in CHS	n	Proportion in CHS
Delta	18–64	F	32,076	0.031	73,217	0.006	990	0.046
		M	28,331	0.049	60,362	0.011	560	0.096
	65–79	F	1,517	0.242	9,908	0.056	771	0.125
		M	1,166	0.317	9,612	0.106	901	0.178
	≥ 80	F	475	0.480	2,121	0.213	697	0.172
		M	246	0.561	1,897	0.308	657	0.253
Omicron	18–64	F	48,370	0.004	80,411	0.003	118,584	0.003
		M	40,347	0.006	64,458	0.004	80,106	0.004
	65–79	F	2,167	0.072	2,405	0.059	23,240	0.024
		M	1,395	0.151	1,658	0.101	19,591	0.043
	≥ 80	F	718	0.306	794	0.188	13,235	0.100
		M	417	0.396	519	0.268	10,196	0.146

CHS: clinical hospital survey; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2.