Table 1.
Baseline characteristics of eligible children enrolled in the study by RSV infection status in infancy. *†
| Baseline characteristic | All (n=1,946) | RSV infection in infancy (n=1,741)* | ||
|---|---|---|---|---|
|
| ||||
| No (n=797) | Yes (n=944) | p-value§ | ||
|
|
|
|
||
| Age at enrollment (days) | 55 (16–78) | 51 (15–75) | 60 (17–86) | 0.005 |
| Female sex | 926 (48%) | 391 (49%) | 436 (46%) | 0.23 |
| Race and ethnicity | 0.004 | |||
| Black non-Hispanic | 343 (18%) | 116 (15%) | 192 (20%) | |
| White non-Hispanic | 1,267 (65%) | 551 (69%) | 580 (61%) | |
| Hispanic | 170 (9%) | 65 (8%) | 91(10%) | |
| Other | 166 (9%) | 65 (8%) | 81 (9%) | |
| RSV season | 0.81 | |||
| 2012–2013 | 858 (44%) | 340 (43%) | 408 (43%) | |
| 2013–2014 | 1,088 (56%) | 457 (57%) | 536 (57%) | |
| Birth month | <0.001 | |||
| June | 270 (14%) | 90 (11%) | 161 (17%) | |
| July | 313 (16%) | 103 (13%) | 179 (19%) | |
| August | 329 (17%) | 141 (18%) | 153 (16%) | |
| September | 261 (13%) | 120 (15%) | 120 (13%) | |
| October | 269 (14%) | 123 (15%) | 106 (11%) | |
| November | 251 (13%) | 114 (14%) | 106 (11%) | |
| December | 253 (13%) | 106 (13%) | 119 (13%) | |
| Gestational age (weeks) | 39 (39–40) | 39 (39–40) | 39 (39–40) | 0.12 |
| Birth weight (grams) | 3,405 (3,120–3,740) | 3,405 (3,120–3,717) | 3,433 (3,121–3,749) | 0.28 |
| Birth by cesarean section | 611 (31%) | 233 (29%) | 325 (34%) | 0.02 |
| Ever breastfeeding | 1,528 (81%) | 653 (82%) | 730 (78%) | 0.07 |
| Daycare attendance in infancy | 590 (34%) | 234 (29%) | 344 (38%) | <0.001 |
| Presence of another child aged <6 years at home during infancy | 983 (51%) | 353 (44%) | 523 (55%) | <0.001 |
| Exposure to secondhand smoking in utero or in early infancy | 425 (22%) | 162 (20%) | 193 (20%) | 0.94 |
| Maternal asthma | 379 (19%) | 160 (20%) | 182 (19%) | 0.67 |
| Type of insurance | 0.13 | |||
| Federal or state | 1,055 (54%) | 402 (50%) | 521 (55%) | |
| Private | 867 (45%) | 384 (48%) | 411 (44%) | |
| Other or Unknown | 24 (2%) | 11 (1%) | 11 (1%) | |
Definition of abbreviations: RSV = Respiratory syncytial virus.
*
Data presented as median (interquartile range) for continuous variables or number (%) for categorical variables.
†
Data calculated for children with complete data.
‡
Of the 1,946 eligible children enrolled in the study, 1,741 (88%) had available data to be classified into one of the two groups.
§
The p-values for the comparison between the groups using a Mann-Whitney U or chi-squared test are shown.