Table 2.
SARS-CoV-2 household infection rate in the full household contacts' cohort and in the serial serology subcohort, stratified by type of exposure to the primary case and household characteristics
|
Full household contacts' cohort (n=414) |
Serial serology sub-cohort (n=134) |
|||||||
|---|---|---|---|---|---|---|---|---|
| Number of PCR-positive/total number | Household infection rate (95% CI) | χ2 test p value* | Number infected/total number | Household infection rate (95% CI) | χ2 test p value* | |||
| Overall | 152/414 | 36·7% (32·2–41·5) | .. | 59/134 | 44·0% (35·9–52·5) | .. | ||
| Contacts' exposure to the primary case | ||||||||
| Relationship status to the primary case | <0·0001 | 0·0016 | ||||||
| Partner, parent to child aged ≤16 years, child aged ≤16 years, or sibling in same bedroom | 85/174 | 48·8% (41·5–56·2) | .. | 36/56 | 64·3% (51·2–75·5) | .. | ||
| Parent to child aged >16 years, child aged >16 years, or sibling without shared bedroom | 39/126 | 30·9% (23·5–39·5) | .. | 11/44 | 25·0% (14·6–39·4) | .. | ||
| Housemate or residential employee | 12/71 | 16·9% (9·9–27·2) | .. | 6/21 | 28·6% (13·8–50·0) | .. | ||
| Data missing | 16/43 | .. | .. | 6/13 | .. | .. | ||
| Primary case SARS-CoV-2 variant | 0·0047 | 0·0016 | ||||||
| Alpha (B.1.1.7) | 56/108 | 51·8% (42·5–61·0) | .. | 25/34 | 73·5% (56·9–85·4) | .. | ||
| Pre-alpha | 31/109 | 28·4% (20·8–37·5) | .. | 11/38 | 28·9% (17·0-44·8) | .. | ||
| Data missing | 65/197 | .. | .. | 23/62 | .. | .. | ||
| Primary case maximum-measured URT RNA viral load, viral copy number per mL | 0·83 | 0·64 | ||||||
| 5 to ≤4500 | 36/82 | 43·9% (33·7–54·7) | .. | 24/47 | 51·1% (37·2–64·7) | .. | ||
| 4500 to ≤12 000 000 | 35/76 | 46·0% (35·3–57·2) | .. | 25/44 | 56·8% (42·2–70·3) | .. | ||
| Data missing | 81/256 | .. | .. | 10/43 | .. | .. | ||
| Contacts' household exposure characteristics | ||||||||
| Number of people resident in the household, including the primary case | 0·22 | 0·44 | ||||||
| 2 people | 25/66 | 37·9% (27·1–49·9) | .. | 12/21 | 57·1% (36·5–75·5) | .. | ||
| 3–4 people | 90/224 | 40·2% (34·0–46·7) | .. | 29/71 | 40·8% (30·2–52·5) | .. | ||
| 5 or more people | 26/96 | 27·1% (19·2–36·7) | .. | 16/35 | 45·7% (30·5–61·8) | .. | ||
| Data missing | 11/28 | .. | .. | 2/7 | .. | .. | ||
| Ratio of the number of people resident in the household per number of bedrooms | 0·065 | 0·23 | ||||||
| ≤1 resident per bedroom | 70/217 | 32·2% (26·4–38·7) | .. | 27/69 | 39·1% (28·5–50·9) | .. | ||
| >1 resident per bedroom | 70/161 | 43·5% (36·1–51·2) | .. | 30/58 | 51·7% (39·2–64·1) | .. | ||
| Data missing | 12/36 | .. | .. | 2/7 | .. | .. | ||
| By household decile of Index of Multiple Deprivation | 0·68 | 0·51 | ||||||
| More deprived deciles, 1 to 5 | 71/200 | 35·5% (29·2–42·3) | .. | 29/71 | 40·8% (30·2–52·5) | .. | ||
| Least deprived deciles, 6 to 10 | 81/214 | 37·8% (31·6–44·5) | .. | 30/63 | 47·6% (35·8–59·7) | .. | ||
Household infection rate is given as the proportion of PCR-positive contacts in the full household contact cohort (n=414), and as the proportion of infected (PCR-positive or seroconverted) contacts in the serial serology subcohort (n=134). Primary case maximum-measured URT RNA viral load categories were divided to give similar number of contacts. URT=upper respiratory tract.
*
p values for each covariate were calculated with the χ2 test accounting for household clustering, applying for all categories where data was available.