Table 1. Baseline characteristics of two-year-old children by seasonal influenza vaccination status, Finland, influenza season 2015/16 (n= 55,258).
| Not vaccinated (N=42,875) |
LAIV vaccinated (N=8,086) |
TIV vaccinated (N=4,297) |
p-valuea | |
|---|---|---|---|---|
| Mother’s age at birthb | ||||
| Years | 30 (5.3) | 31 (5.0) | 31 (5.0) | <0.001 |
| Socio-economic status based on mother’s occupationc,e | ||||
| Higher white-collar workers | 8,596 (20.0) | 2,158 (26.7) | 1,145 (26.6) | <0.001 |
| Lower white-collar workers | 18,375 (42.9) | 3,329 (41.2) | 1,760 (41.0) | |
| Blue-collar workers | 7,069 (16.5) | 934 (11.6) | 516 (12.0) | |
| Others | 8,835 (20.6) | 1,665 (20.6) | 876 (20.4) | |
| Mother’s marital statusd | ||||
| Single or divorced | 4,202 (9.8) | 620 (7.7) | 334 (7.8) | <0.001 |
| Cohabiting | 14,830 (34.6) | 2,408 (29.8) | 1,210 (28.2) | |
| Married | 23,843 (55.6) | 5,058 (62.6) | 2,753 (64.1) | |
| Mother’s smoking behaviourd | ||||
| No | 35,303 (82.3) | 7,284 (90.1) | 3,867 (90.0) | <0.001 |
| Quitted during first trimester | 3,232 (7.5) | 427 (5.3) | 210 (4.9) | |
| Continued after first trimester | 4,340 (10.1) | 375 (4.6) | 220 (5.1) | |
| Birth weightb,d | ||||
| Grams | 3,514 (541.8) | 3,470 (579.7) | 3,459 (595.1) | <0.001 |
| Gestational age at birthd | ||||
| <28 weeks | 68 (0.2) | 35 (0.4) | 30 (0.7) | <0.001 |
| ≥28 and <37 weeks | 4,173 (9.7) | 903 (11.2) | 504 (11.7) | |
| ≥37 weeks | 38,634 (90.1) | 7,148 (88.4) | 3,763 (87.6) | |
| Number of siblings at birthc | ||||
| 0 | 16,156 (37.7) | 4,057 (50.2) | 1,830 (42.6) | <0.001 |
| 1 | 15,116 (35.3) | 2,465 (30.5) | 1,509 (35.1) | |
| >1 | 11,603 (27.1) | 1,564 (19.3) | 958 (22.3) | |
| Month of birthc | ||||
| January–June | 22,169 (51.7) | 3,424 (42.3) | 1,967 (45.8) | <0.001 |
| July–December | 20,706 (48.3) | 4,662 (57.7) | 2,330 (54.2) | |
| Sexc | ||||
| Male | 21,870 (51.0) | 4,225 (52.3) | 2,302 (53.6) | 0.001 |
| Female | 21,005 (49.0) | 3,861 (47.7) | 1,995 (46.4) | |
| Nationalityc | ||||
| Finnish | 39,483 (92.1) | 7,682 (95.0) | 4,013 (93.4) | <0.001 |
| Non-Finnish | 3,392 (7.9) | 404 (5.0) | 284 (6.6) | |
| Place of residencec | ||||
| Urban | 29,709 (69.3) | 6,220 (76.9) | 3,368 (78.4) | <0.001 |
| Semi-urban | 7,713 (18.0) | 1,125 (13.9) | 517 (12.0) | |
| Rural | 5,453 (12.7) | 741 (9.2) | 412 (9.6) | |
| BCG vaccination statusc | ||||
| Not vaccinated | 39,403 (91.9) | 7,618 (94.2) | 3,988 (92.8) | <0.001 |
| Vaccinated | 3,472 (8.1) | 468 (5.8) | 309 (7.2) | |
| Presence of underlying chronic conditionsc | ||||
| No | 37,734 (88.0) | 7,032 (87.0) | 3,510 (81.7) | <0.001 |
| Yes | 5,141 (12.0) | 1,054 (13.0) | 787 (18.3) | |
| Presence of an acute disease between week 14–39, 2015c | ||||
| No | 39,766 (92.7) | 7,354 (90.9) | 3,791 (88.2) | <0.001 |
| Yes | 3,109 (7.3) | 732 (9.1) | 506 (11.8) | |
| SIV vaccination status in2013/14 and 2014/15c,f | ||||
| Not vaccinated | 38,288 (89.3) | 3,470 (42.9) | 1,386 (32.3) | <0.001 |
| Vaccinated | 4,587 (10.7) | 4,616 (57.1) | 2,911 (67.7) | |
BCG: Bacillus Calmette–Guérin vaccine: LAIV: live attenuated influenza vaccine; TIV: trivalent inactivated influenza vaccine; SIV: seasonal influenza vaccine.
a One-way analysis of variance for continuous and chi-squared test of independence for categorical variables.
b Mean (standard deviation).
c Absolute frequency (relative frequency in %). Because of rounding, percentages may not total 100.
d Proportion of data imputed by hot deck imputation: <0.2%.
e Proportion of data imputed by hot deck imputation: 31.5%.
f Vaccinated group contains those vaccinated either in the 2013/14, 2014/15 season or both.