Table 3.

Group-specific attack rates and risk factors for SAR-CoV-2 infection among close contacts

	Number of cases*	Number infected	Attack rate (95% CI)	Univariate regression			Multivariate regression
				Odds ratio	2·5%	97·5%	Odds ratio	2·5%	97·5%
Sex
Female	558	58	10·4% (8·1–13·2)	Ref	..	..	..	..	..
Male	486	26	5·3% (3·7–7·7)	0·43	0·21	0·86	..	..	..
Age
0–9 years	148	11	7·4% (4·2–12·8)	2·33	0·38	14·05	..	..	..
10–19 years	85	6	7·1% (3·3–14·6)	3·50	0·53	23·24	..	..	..
20–29 years	114	7	6·1% (3·0–12·1)	4·91	0·74	32·64	..	..	..
30–39 years	268	16	6·0% (3·7–9·5)	1·84	0·34	9·80	..	..	..
40–49 years	143	7	4·9% (2·4–9·8)	3·46	0·55	21·92	..	..	..
50–59 years	110	10	9·1% (5·0–15·9)	Ref	..	..	..	..	..
60–69 years	130	20	15·4% (10·2–22·6)	5·68	1·01	32·09	..	..	..
≥70 years	72	7	9·7% (4·8–18·7)	4·26	0·64	28·44	..	..	..
Contact type: household
No	456	4	0·9% (0·3–2·2)	Ref	..	..	Ref	..	..
Yes	686	77	11·2% (9·1–13·8)	15·10	3·69	61·69	6·27	1·49	26·33
Contact type: travel
No	824	63	7·6% (6·0–9·7)	Ref	..	..	Ref	..	..
Yes	318	18	5·7% (3·6–8·8)	9·13	1·85	45·08	7·06	1·43	34·91
Contact type: meal
No	435	20	4·6% (3·0–7·0)	Ref	..	..	Ref	..	..
Yes	707	61	8·6% (6·8–10·9)	23·01	2·51	211·2	7·13	0·73	69·32
Contact frequency
Rare	230	1	0·4% (0·02–2·4)	<0·0001	0	Inf	..	..	..
Moderate	305	9	3·0% (1·6–5·5)	Ref	..	..	..	..	..
Often	555	71	12·8% (10·3–15·8)	8·8	2·58	30·06	..	..	..

SARS-CoV-2=severe acute respiratory syndrome coronavirus 2. Inf=infinity.

^*15 confirmed close contacts were excluded from this analysis because contact tracing reports for the negative close contacts in the same clusters were missing. Close contacts with missing data on sex, age, contact types, or contact frequency not shown.