Table 1. Crude Seroprevalence and Seroprevalence Differences and Ratios for Children Aged 2 to 17 Years by Individual and Household Characteristics, October 2020 to March 2021 in Montreal, Canada.
| Demographic characteristics | Children, No./total No. (%) | Seroprevalence, % (95% CI) | Crude prevalence ratio (95% CI) | |
|---|---|---|---|---|
| Seronegative | Seropositive | |||
| Total | 1537 | 95 | 5.8 (4.6 to 7.0) | NA |
| Sex | ||||
| Female | 746/1537 (49) | 55/95 (58) | 6.9 (4.9 to 8.8) | 1 [Reference] |
| Male | 797/1537 (51) | 40/95 (42) | 4.8 (3.2 to 6.4) | 0.7 (0.4 to 1.0) |
| Age, y | ||||
| 2-4 | 316/1529 (21) | 16/95 (17) | 4.8 (2.9 to 6.7) | 1 [Reference] |
| 5-9 | 515/1529 (34) | 27/95 (28) | 5.0 (3.4 to 6.6) | 1.0 (0.5 to 1.5) |
| 10-14 | 493/1529 (32) | 36/95 (38) | 6.8 (4.2 to 9.4) | 1.4 (0.6 to 2.2) |
| 15-17 | 205/1529 (13) | 16/95 (17) | 7.2 (3.4 to 11.0) | 1.5 (0.5 to 2.5) |
| Child attending | ||||
| Day care | 335/1537 (22) | 19/95 (20) | 5.4 (3.3 to 7.4) | 1 [Reference] |
| Primary school | 686/1537 (45) | 39/95 (41) | 5.4 (4.1 to 6.6) | 1.0 (0.6 to 1.5) |
| Secondary school | 516/1537 (34) | 37/95(39) | 6.7 (3.8 to 9.6) | 1.3 (0.5 to 2.0) |
| BMI | ||||
| Underweight or normal weight | 1208/1520 (79) | 80/95 (84) | 6.2 (4.9 to 7.5) | 1 [Reference] |
| Overweight or obesity | 312/1520 (21) | 15/95 (16) | 4.6 (2.3 to 6.9) | 0.7 (0.4 to 1.1) |
| Born premature | ||||
| No | 1447/1520 (95) | 87/93 (94) | 5.7 (4.5 to 6.9) | 1 [Reference] |
| Yes (<37 wk) | 73/1520 (5) | 6/93 (6) | 7.6 (1.9 to 13.3) | 1.3 (0.3 to 2.4) |
| Chronic medical conditions | ||||
| None | 1427/1525 (94) | 90/95 (95) | 5.9 (4.7 to 7.2) | 1 [Reference] |
| Asthma | 48/1525 (3) | 4/95 (4) | 7.4 (0.5 to 14.3) | 1.3 (0.1 to 2.4) |
| Other conditions | 50/1525 (3) | 1/95 (1) | 2.0 (−2.0 to 6.1) | 0.3 (−0.4 to 1.0) |
| Neighborhood | ||||
| West Island | 487/1537 (32) | 17/95 (18) | 3.4 (2.4 to 4.3) | 1 [Reference] |
| Mercier-Hochelaga-Maisonneuve | 329/1537 (21) | 28/95 (29) | 7.8 (5.2 to 10.5) | 2.3 (1.3 to 3.4) |
| Montreal North | 215/1537 (14) | 22/95 (23) | 9.3 (6.4 to 12.2) | 2.8 (1.6 to 3.9) |
| Plateau-Mont-Royal | 506/1537 (33) | 28/95 (29) | 5.3 (3.5 to 7.0) | 1.6 (0.9 to 2.3) |
| Parental respondent’s level of education | ||||
| <Bachelor’s degree | 366/1517 (24) | 18/95 (19) | 4.7 (2.6 to 6.8) | 1 [Reference] |
| Bachelor’s degree | 606/1517 (40) | 41/95 (43) | 6.3 (4.5 to 8.2) | 1.4 (0.8 to 2.0) |
| ≥Master’s degree | 545/1517 (36) | 36/95 (38) | 6.2 (4.2 to 8.2) | 1.3 (0.6 to 2.1) |
| Parental respondent’s race and ethnicity | ||||
| Racial or ethnic minority | 179/1512 (12) | 22/95 (23) | 11.0 (6.9 to 15.1) | 2.1 (1.1 to 3.1) |
| White | 1333/1512 (88) | 73/95 (77) | 5.2 (3.9 to 6.4) | 1 [Reference] |
| Adults in household, No. | ||||
| 1 | 182/1526 (12) | 10/95 (11) | 5.2 (1.8 to 8.6) | 1 [Reference] |
| 2 | 1188/1526 (78) | 70/95 (74) | 5.6 (4.2 to 6.9) | 1.1 (0.3 to 1.8) |
| ≥3 | 156/1526 (10) | 15/95 (16) | 8.8 (4.7 to 12.9) | 1.7 (0.4 to 3.0) |
| Children in household, No. | ||||
| 1 | 326/1526 (21) | 24/95 (25) | 6.9 (3.7 to 10.1) | 1 [Reference] |
| 2 | 834/1526 (55) | 44/95 (46) | 5.0 (3.6 to 6.5) | 0.7 (0.3 to 1.1) |
| ≥3 | 366/1526 (24) | 27/95 (28) | 6.9 (4.3 to 9.4) | 1.0 (0.4 to 1.6) |
| Bedrooms in household, No. | ||||
| 1-2 | 314/1526 (21) | 18/95 (19) | 5.4 (3.2 to 7.7) | 1 [Reference] |
| 3-4 | 1112/1526 (73) | 73/95 (77) | 6.2 (4.8 to 7.5) | 1.1 (0.6 to 1.6) |
| ≥5 | 100/1526 (7) | 4/95 (4) | 3.8 (0 to 7.9) | 0.7 (−0.1 to 1.5) |
| Any household member working in | ||||
| Other occupations | 869/1526 (57) | 44/95 (46) | 4.8 (3.5 to 6.2) | 1 [Reference] |
| Essential occupation other than health care | 132/1526 (9) | 17/95 (18) | 6.8 (3.8 to 9.8) | 1.4 (0.7 to 2.2) |
| Health care | 525/1526 (34) | 34/95 (36) | 7.9 (5.0 to 10.7) | 1.6 (0.8 to 2.4) |
| Household member has underlying health issues that may put them at higher risk if exposed to COVID-19 | ||||
| No | 1275/1526 (84) | 83/95 (87) | 6.2 (4.9 to 7.5) | 1 [Reference] |
| Yes | 251/1526 (16) | 12/95 (13) | 4.6 (1.3 to 7.9) | 0.7 (0.2 to 1.3) |
| Child had positive COVID-19 diagnosis via RT-PCR prior to serology testinga | ||||
| No | ||||
| Child was not tested | 829/1535 (54) | 48/95 (51) | 5.5 (4.2 to 6.7) | 1 [Reference] |
| All tests negative | 697/1535 (45) | 30/95 (32) | 4.1 (2.7 to 5.5) | 0.8 (0.4 to 1.1) |
| Yes, at least 1 positive test | 9/1535 (1) | 17/95 (18) | 65.4 (44.9 to 85.9) | 11.9 (7.7 to 16.2) |
| Household member other than child had confirmed COVID-19 infection via RT-PCR | ||||
| No | 1475/1526 (97) | 71/95 (75) | 4.6 (3.6 to 5.6) | 1 [Reference] |
| Yes | 51/1526 (3) | 24/95 (25) | 32.0 (19.9 to 44.1) | 7.0 (3.9 to 10.0) |
Abbreviations: BMI, body mass index; NA, not applicable; RT-PCR, reverse transcriptase–polymerase chain reaction.
a
Median time between RT-PCR positive test and serology test was 109 days (IQR, 66-146 days).