. 2022 May 5;27(18):2200322. doi: 10.2807/1560-7917.ES.2022.27.18.2200322

Table 1. Characteristics of severe COVID-19 cases (n = 593) and controls (n = 5,930), stratified by follow-up period for monitoring of vaccine effectiveness during SARS-CoV-2 Omicron variant dominance, Scania, Sweden, 2021 week 52–2022 week 11 .

Characteristics	Follow-up period
	Omicron BA.1 2021 w52–2022 w1				Transition 2022 w2–3				Omicron BA.2 2022 w4–11
	Cases (n = 129)		Controls (n = 1,290)		Cases (n = 156)		Controls (n = 1,560)		Cases (n = 308)		Controls (n = 3,080)
Weekly case rate, mean (n)	65		NA		78		NA		56^a		NA
Age group (years)	%	n	%	n	%	N	%	n	%	n	%	n
0–17	3.1	4	3.6	47	5.1	8	4.3	67	5.2	16	5.1	156
18–39	16	21	15	198	9.0	14	10	157	12	37	12	364
40–64	30	39	30	392	23	36	24	367	15	47	17	523
≥ 65	50	65	51	653	63	98	62	969	68	208	66	2,037
Sex
Female	37	48	37	480	38	60	38	600	50	153	50	1,530
Male	63	81	63	810	62	96	62	960	50	155	50	1,550
Born abroad	46	60	22	277	32	50	20	309	23	70	18	561
Civil status
Married	45	58	47	611	36	56	48	746	37	113	47	1,460
Widow/widower	8.5	11	8.8	114	15	24	11	176	16	48	15	462
Divorced	21	27	15	197	21	33	17	259	23	70	14	443
Single	26	33	28	368	28	43	24	379	25	77	23	715
Comorbidities
0	36	46	63	816	38	59	58	905	33	103	56	1,736
1	26	33	21	273	26	40	23	362	25	78	25	758
≥ 2	39	50	16	201	36	57	19	293	41	127	19	586
Vaccine doses
0	54	70	14	185	42	65	13	201	27	82	13	394
1	3.1	4	1.8	23	4.5	7	1.8	28	4.5	14	1.6	50
2	18	23	37	481	28	44	29	459	20	62	17	519
3	25	32	47	601	26	40	56	872	49	150	68	2,108
4	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.3	9
Vaccine type^b
Comirnaty	74	41	72	775	71	60	70	934	73	155	69	1,825
Spikevax	3.6	2	6.7	73	13	11	4.9	65	4.7	10	4.3	114
Vaxzevria	3.6	2	2.3	25	4.8	4	2.0	27	2.4	5	1.0	26
Mixed	18	10	19	209	11	9	23	305	20	42	26	671
Time since last vaccine dose^b (months)
0–3	54	30	60	650	43	36	66	884	38	80	56	1,470
3–6 months	20	11	27	288	27	23	19	256	43	92	35	933
≥ 6 months	26	14	13	144	30	25	14	191	19	40	8.8	233
Prior SARS-CoV-2 infection	2.3	3	8.8	114	3.8	6	8.2	128	5.8	18	8.1	250
At least two doses or prior SARS-CoV-2 infection	43	56	85	1,101	54	85	87	1,353	70	216	87	2,675

COVID-19: coronavirus disease; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2.

^a Last two weeks of the Omicron BA.2 was not included in the calculation of weekly case rate in order to limit the impact of delay in manifestation of severe cases.

^b Only persons with at least two doses.

A severe COVID-19 case was defined as a case who was hospitalised for at least 24 h from 5 days before until 14 days after a positive SARS-CoV-2 test and required oxygen supply (≥ 5 L/min) or admittance to an intensive care unit (ICU). For each severe case, 10 controls without a positive test the same week as the case or 90 days prior were randomly selected from the underlying study cohort, matched with respect to sex and age (5-year groups).