Table 1.
Serology Test Result According to General Characteristics and Medical History, Stratified by Type of Participant (Unadjusted Results)
| Index Cases (n = 219) | Household Members (n = 302) | Close Contacts Outside the Household (n = 69) | |||||
|---|---|---|---|---|---|---|---|
| No. (%) Seropositive | No. (%) Seropositive | Unadjusted OR [95% CI] | P Value | No. (%) Seropositive | Unadjusted OR [95% CI] | P Value | |
| All participants | 215/219 (98.2) | 160/302 (53.0) | 12/69 (17.4) | ||||
| Age | .119 | .928 | |||||
| 6 mo–<5 y | 1/2 (50.0) | 5/11 (45.5) | 0.92 [0.37–2.29] | No participant | ·· | ||
| 5 y–<10 y | 1/1 (100.0) | 12/22 (54.6) | 1.16 [0.55–2.44] | 0/1 (0.0) | ·· | ||
| 10 y–<15 y | 2/2 (100.0) | 15/32 (46.9) | 0.93 [0.49–1.75] | 0/3 (0.0) | ·· | ||
| 15 y–<20 y | 20/21 (95.2) | 9/19 (47.4) | 1.17 [0.56–2.45] | 0/2 (0.0) | ·· | ||
| 20 y–<40 y | 42/43 (97.7) | 37/76 (48.7) | Reference | 3/15 (20.0) | Reference | ||
| 40 y–<65 y | 103/104 (99.0) | 60/116 (51.7) | 0.83 [0.52–1.30] | 7/38 (18.4) | 0.92 [0.22–3.87] | ||
| 65 y–<75 y | 31/31 (100.0) | 12/14 (85.7) | 3.98 [1.03–15.44] | 2/9 (22.2) | 1.32 [0.16–11.00] | ||
| ≥75 y | 15/15 (100.0) | 10/12 (83.3) | 5.25 [1.16–23.72] | 0/1 (0.0) | ·· | ||
| Gender | .164 | .124 | |||||
| Male | 94/96 (97.9) | 74/146 (50.7) | Reference | 8/30 (26.7) | Reference | ||
| Female | 120/122 (98.4) | 86/156 (55.1) | 1.27 [0.91–1.76] | 4/39 (10.3) | 0.36 [0.10–1.32] | ||
| Other | 1/1 (100.0) | No participant | ·· | No participant | ·· | ||
| Current smokera | .034 | .825 | |||||
| No | 191/194 (98.5) | 142/256 (55.5) | Reference | 10/59 (17.0) | Reference | ||
| Yes | 23/24 (95.8) | 18/46 (39.1) | 0.56 [0.32–0.96] | 2/9 (22.2) | 1.21 [0.22–6.53] | ||
| Weight status | .146 | .011 | |||||
| Normal or underweight | 104/106 (98.1) | 92/184 (50.0) | Reference | 2/35 (5.7) | Reference | ||
| Overweight or obese | 110/112 (98.2) | 66/111 (59.5) | 1.37 [0.90–2.09] | 10/33 (30.3) | 6.74 [1.54–29.50] | ||
| Adult participants only | |||||||
| Education | .196 | .423 | |||||
| Lower secondary or less | 21/21 (100.0) | 21/33 (63.6) | Reference | 3/10 (30.0) | Reference | ||
| Upper secondary | 58/59 (98.3) | 46/82 (56.1) | 0.93 [0.46–1.90] | 5/23 (21.7) | 0.64 [0.13–3.21] | ||
| Tertiary | 108/109 (99.1) | 51/100 (51.0) | 0.61 [0.30–1.24] | 4/30 (13.3) | 0.33 [0.06–1.83] | ||
| Chronic medical conditionsb | .037 | .148 | |||||
| None | 131/133 (98.5) | 86/169 (50.9) | Reference | 6/44 (13.6) | Reference | ||
| ≥1 | 58/58 (100.0) | 32/47 (68.1) | 1.94 [1.04–3.62] | 6/19 (31.6) | 2.48 [0.73–8.48] | ||
| Hypertension | .110 | .034 | |||||
| No | 152/154 (98.7) | 95/182 (52.2) | Reference | 7/50 (14.0) | Reference | ||
| Yes | 36/36 (100.0) | 21/31 (67.7) | 1.81 [0.87–3.74] | 5/11 (45.5) | 4.48 [1.12–18.01] | ||
| Diabetes | .489 | .082 | |||||
| No | 169/171 (98.8) | 111/206 (53.9) | Reference | 10/57 (17.5) | Reference | ||
| Yes | 15/15 (100.0) | 4/6 (66.7) | 1.75 [0.36–8.48] | 2/3 (66.7) | 8.59 [0.76–96.92] | ||
| Cardiovascular disease | .239 | ·· | |||||
| No | 170/172 (98.8) | 103/196 (52.6) | Reference | 12/58 (20.7) | ·· | ||
| Yes | 12/12 (100.0) | 9/12 (75.0) | 2.03 [0.62–6.62] | 0/2 (0.0) | ·· | ||
| Kidney disease | |||||||
| No | 181/183 (98.9) | 115/212 (54.3) | ·· | 12/60 (20.0) | ·· | ||
| Yes | 3/3 (100.0) | No participant | ·· | 0/1 (0.0) | ·· | ||
| Chronic respiratory disease | .196 | ·· | |||||
| No | 177/179 (98.9) | 106/202 (52.5) | Reference | 12/59 (20.3) | ·· | ||
| Yes | 7/7 (100.0) | 4/5 (80.0) | 3.79 [0.50–28.52] | 0/2 (0.0) | ·· | ||
| Immunodeficiency | .596 | ·· | |||||
| No | 174/176 (98.9) | 110/202 (54.5) | Reference | 12/58 (20.7) | ·· | ||
| Yes | 12/12 (100.0) | 4/9 (44.4) | 0.74 [0.25–2.23] | 0/3 (0.0) | ·· | ||
| Cancer | |||||||
| No | 177/179 (98.9) | 113/209 (54.1) | ·· | 12/58 (20.7) | ·· | ||
| Yes | 4/4 (100.0) | No participant | ·· | 0/2 (0.0) | ·· | ||
| Other chronic condition | .325 | ·· | |||||
| No | 159/160 (99.4) | 97/184 (52.7) | Reference | 12/55 (21.8) | ·· | ||
| Yes | 24/25 (96.0) | 18/28 (64.3) | 1.49 [0.68–3.27] | 0/7 (0.0) | ·· | ||
Calculation of odds ratio and P value: correlation between close contacts of the same index case taken into account using GEE (exchangeable correlation structure, logit link function).
Abbreviations: GEE, generalized estimating equation; OR, odds ratio.
aChildren aged <12 considered nonsmokers.
bAmong all following conditions, except “other chronic condition.”