Table 2.
Characteristics of the screened children, by serological status
| Seronegative children (n=313) | Seropositive children (n=14) | Relative risk or mean difference (95% CI) | ||
|---|---|---|---|---|
| Sex | ||||
| Female | 155/313 (49%) | 5/14 (36%) | .. | |
| Male | 158/313 (51%) | 9/14 (64%) | 1·3 (0·4 to 3·9) | |
| Age, years | 1·9 (0·9) | 1·7 (0·8) | −0·2 (−0·6 to 0·2) | |
| History of recurrent bronchiolitis or wheezing | 86/312 (28%) | 3/14 (21%) | 0·8 (0·2 to 2·9) | |
| Gestational age at birth, weeks | 39 (1·7) | 39 (1·9) | 0 (−1 to 1) | |
| Birthweight, Z score | −0·05 (1·04) | −0·07 (0·91) | 0 (−0·5 to 0·5) | |
| Ability to walk | 221/311 (73%) | 10 (71%) | 1·0 (0·3 to 3·2) | |
| Attendance at another type of care facility | 61/312 (20%) | 2/14 (14%) | 0·7 (0·2 to 3·4) | |
| Number of adults at home | 2·0 (0·6) | 2·1 (0·6) | 0·1 (−0·2 to 0·4) | |
| Number of children at home, including the study participant | 1·8 (0·8) | 1·5 (0·7) | −0·3 (−0·7 to 0·1) | |
| History of fever (body temperature >38°C) during lockdown* | 70/292 (24%) | 5/14 (36%) | 1·5 (0·5 to 4·5) | |
| History of respiratory signs (dyspnoea, cough, rhinitis, otitis, or conjunctivitis) during lockdown* | 96/291 (33%) | 6/12 (50%) | 1·4 (0·5 to 4·1) | |
| History of abdominal signs (diarrhoea, vomiting, or abdominal pain) during lockdown* | 57/300 (19%) | 2/13 (15%) | 0·8 (0·2 to 3·6) | |
| Exclusion from the daycare centre due to clinical signs during lockdown | 49/311 (16%) | 2 (14%) | 0·9 (0·2 to 4·2) | |
| RT-PCR testing of a nasal swab during lockdown* | 15/313 (5%) | 1 (7%) | 1·5 (0·2 to 12·2) | |
| Positive RT-PCR test during lockdown* | 0 | 0 | .. | |
| Contact with a confirmed case of COVID-19 during lockdown* | 38/307 (12%) | 6/14 (43%) | 3·5 (1·2 to 10·7) | |
| At least one child from the daycare centre | 7/307 (2%) | 1/14 (7%) | 3·2 (0·4 to 27·9) | |
| At least one daycare centre staff member | 7/307 (2%) | 1/14 (7%) | 3·2 (0·4 to 27·9) | |
| At least one other child living with the child | 1/307 (<1%) | 0 | 0 | |
| At least one adult living with the child | 19/307 (6%) | 6/14 (43%) | 7·1 (2·2 to 22·4) | |
| Mean number of days of attendance at a daycare centre during lockdown* | 20 (12) | 19 (12) | −1 (−7 to 5) | |
| Attendance at a daycare centre operated by a hospital† | 250/313 (80%) | 9/14 (64%) | 0·8 (0·3 to 2·5) | |
| Mean number of children attending the centre per day | 29 (11) | 25 (12) | −4 (−10·4 to 2·4) | |
| Parents' occupation | ||||
| At least one health-care worker in a dedicated COVID-19 unit | 94/313 (30%) | 3/14 (21%) | 0·7 (0·2 to 2·6) | |
| At least one health-care worker in a non-COVID-19 unit | 167/313 (53%) | 8/14 (58%) | 1·1 (0·4 to 3·2) | |
| Other occupations | 52/313 (17%) | 3/14 (21%) | 1·3 (0·3 to 4·8) | |
| Serological testing of parents | ||||
| At least one seropositive parent‡ (n=170) | 22/149 (14%) | 6/11 (55%) | 6·1 (1·9 to 19·1) | |
| Serological testing of daycare centre staff§ | ||||
| At least one seropositive staff member (n=312) | 133/299 (44%) | 8/13 (62%) | 1·9 (0·7 to 5·8) | |
Data are n/N (%), or mean (SD), unless otherwise indicated. Missing data for seronegative children: gestational age at birth (n=6), birthweight Z score (n=7), and number of days of daycare centre attendance (n=4).
*
Between March 15 and May 9, 2020.
†
Daycare centres not operated by a hospital were operated by a local authority.
‡
SARS-CoV-2 serological status retrospectively determined in an ELISA (based on detection of IgG or total immunoglobulin).
§
Biosynex COVID-19 BSS test (Biosynex, Illkirch-Graffenstaden, France).