Table 1.
Characteristics of participants in the summer school longitudinal study. All individuals with at least one saliva sample of sufficient volume available are included
| Initial visit | Final visit | Single visit | |
|---|---|---|---|
| (N=1568) | (N=1568) | (N=339) | |
| Age continuous mediana | 8.0 (5.0-14.0) | 7.0 (5.0-10.0) | |
| Age stratifiedb | |||
| Children | 1181 (75.3%) | 316 (93.2%) | |
| Adults | 387 (24.7%) | 23 (6.8%) | |
| Sex | |||
| Male | 756 (48.2%) | 184 (54.3%) | |
| Female | 812 (51.8%) | 155 (45.7%) | |
| Dates collectionc | |||
| 1st week | 465 (29.7%) | 0 (0.0%) | 59 (17.4%) |
| 2nd week | 873 (55.7%) | 46 (2.9%) | 175 (51.3%) |
| 3rd week | 216 (13.8%) | 385 (24.6%) | 73 (21.5%) |
| 4th week | 14 (0.9%) | 603 (38.5%) | 25 (7.4%) |
| 5th week | 0 (0.0%) | 535 (34.1%) | 8 (2.4%) |
| SARS-CoV-2 RT-PCRd | |||
| Positive | 2 (0.1%) | 7 (0.4%) | 2 (0.6%) |
| Negative | 1552 (99.2%) | 1557 (99.5%) | 335 (98.8%) |
| Indeterminate | 1 (0.1%) | 1 (0.1%) | 0 (0.0%) |
| Not valid | 9 (0.6%) | 0 (0.0%) | 2 (0.6%) |
| Symptoms | |||
| Yes | 71 (4.5%) | 76 (4.8%) | 16 (4.7%) |
| Children | 62 (5.2%) | 65 (5.5%) | 16 (5.1%) |
| Adults | 9 (2.3%) | 11 (2.8%) | 0 (0.0%) |
| No | 1492 (95.2%) | 1492 (95.2%) | 323 (95.3%) |
| Children | 1119 (94.8%) | 1116 (94.5%) | 300 (94.9%) |
| Adults | 378 (97.7%) | 376 (97.2%) | 23 (100%) |
aMissing age of 9 adults. IQR in parenthesis
bAdult: Age 15 years or older
cAverage (median) time in days between initial and final visit was 14 (SD 6.69, IQR 7.0–21.0); 15.69 (SD 6.44, IQR 10–21) if only those with ≥ 6 days between visits are included
dIn the saliva antibody study cohort, there were 7 children and 3 adults who tested RT-PCR positive. Among them, one child and one adult were single visits. There was one adult who was positive at the first visit and negative at the last visit, and one child who was positive at both visits; therefore there were 11 positive samples. Among the paired samples, there were 8 with a positive RT-PCR at any timepoint (6 children, 2 adults). In the main infection cohort study [25], 12 participants (9 children among them) were positive by RT-PCR at least in one visit, and from 11 of them there was a saliva sample available for serology. 3446 samples were RT-PCR negative, 2 indeterminate, 11 invalid, and 7 non-available. Only 5 adults have had COVID-19 before the study