Table 2. Crude and adjusted risk factors for infection among contacts in the Omicron-dominant period in a study of SARS-CoV-2 secondary attack rates in vaccinated and unvaccinated household contacts during replacement of Delta with Omicron variant, Spain*.

Variable	No. patients†	Crude OR			Adjusted OR‡
		OR (95% CI)	p value		OR (95% CI)	p value
Vaccination status, contacts
Vaccinated	135/170	Referent			Referent
Unvaccinated	39/45	1.69 (0.7–4.3)	0.3		1.86 (0.6–6.2)	0.3
1 dose	25/29	Referent			Referent
2 doses	90/113	0.63 (0.2–2.0)	0.4		0.75 (0.2–2.9)	0.7
3 doses	19/27	0.38 (0.1–1.5)	0.2		0.36 (0.1–1.9)	0.2
Missing data	1/1
Time since vaccination, wk
1–13	36/48	Referent			Referent
14–20	28/35	1.33 (0.5–3.8)	0.6		2.17 (0.5–9.3)	0.3
21–25	34/41	1.62 (0.6–4.6)	0.4		2.41 (0.7–7.8)	0.1
>25	36/45	1.33 (0.5–3.6)	0.6		1.91 (0.6–5.7)	0.2
Missing data	1/1
Pooled		1.12 (0.8–1.5)	0.5		1.26 (0.9–1.8)	0.2
Age of contacts, y
0–12	36/42	Referent			Referent
13/18	22/27	0.73 (0.2–2.7)	0.6		0.99 (0.2–4.4)	0.9
19/35	38/47	0.70 (0.2–2.2)	0.5		0.94 (0.2–3.8)	0.9
36/45	33/42	0.61 (0.2–1.9)	0.4		0.83 (0.2–3.3)	0.8
>45	45/57	0.63 (0.2–1.8)	0.4		0.82 (0.2–3.2)	0.8
Pooled		0.90 (0.7–1.1)	0.4		0.94 (0.7–1.2)	0.6
Vaccination status, index patients
Vaccinated	134/161	Referent			Referent
Unvaccinated	40/54	0.56 (0.3–1.2)	0.1		0.98 (0.2–3.9)	0.9
Age of index patients, y
0–12	36/50	Referent			Referent
13–18	13/15	2.53 (0.5–12.7)	0.3		2.79 (0.4–20.4)	0.3
19–35	35/44	1.51 (0.6–3.9)	0.4		1.47 (0.4–5.8)	0.6
36–45	51/59	2.48 (0.9–6.5)	0.07		2.27 (0.5–10.5)	0.3
>45	39/47	1.90 (0.7–5.0)	0.2		1.84 (0.4–8.8)	0.4
Pooled		1.20 (0.9–1.5)	0.1		1.09 (0.8–1.5)	0.6
Number of housemates
<2	60/70	Referent			Referent
>2	114/145	0.61 (0.3–1.3)	0.2		0.62 (0.3–1.4)	0.3
Sex
M	93/115	Referent			Referent
F	81/100	1.13 (0.7–1.9)	0.6		0.97 (0.5–2.0)	0.9

*OR, odds ratio. †Values are number infected/total number of patients in each strata. ‡Adjusted analysis only included participants who had all data available.