TABLE 1.
Demographic characteristics of postpartum women by influenza vaccination status, N=4084, Cape Town, South Africa, 2015‐2016
| Characteristic |
All N = 4084 |
Vaccinated n = 2109 (51.6%) |
Unvaccinated n = 1975 (48.4%) |
P value | Standardized difference | IPTW weighted standardized difference § |
|---|---|---|---|---|---|---|
| Maternal age in years, n/N (%) | ||||||
| <20 | 440 (10.8) | 217 (10.3) | 223 (11.3) | 0.022 | 0.055 | 0.043 |
| 20‐24 | 1196 (29.3) | 660 (31.3) | 536 (27.1) | |||
| 25‐29 | 1177 (28.8) | 605 (28.7) | 572 (29.0) | |||
| 30‐34 | 794 (19.4) | 403 (19.1) | 391 (19.8) | |||
| ≥35 | 477 (11.7) | 224 (10.6) | 253 (12.8) | |||
| Mean age in years (range) | 26.7 (13‐47) | 26.5 (13‐45) | 27.0 (13‐47) | 0.013 | ||
| Campaign year, n (%) | ||||||
| 2015 | 2195 (53.7) | 1113 (52.8) | 1082 (54.8) | 0.198 | 0.059 | 0.079 |
| 2016 | 1889 (46.3) | 996 (47.2) | 893 (45.2) | |||
| Season of infant birth, n (%) | ||||||
| Before influenza season | 327 (8.0) | 172 (8.2) | 155 (7.8) | <0.001 | 0.341 | 0.323 |
| During influenza season | 1130 (27.7) | 801 (38.0) | 329 (16.7) | |||
| After influenza season | 2627 (64.3) | 1136 (53.9) | 1491 (75.5) | |||
| Site, n (%) | ||||||
| Mitchell’s Plain Maternal | 1436 (35.2) | 745 (35.3) | 691 (35.0) | <0.001 | 0.007 | 0.014 |
| Obstetric Unit | ||||||
| Mitchell’s Plain District Hospital | 1633 (40.0) | 937 (44.4) | 696 (35.2) | |||
| Mowbray Maternity Hospital | 714 (17.5) | 337 (16.0) | 377 (19.1) | |||
| Groote Schuur Hospital | 301 (7.4) | 90 (4.3) | 211 (10.7) | |||
| Pregnancy history | ||||||
| Gravidity, n/N (%) | ||||||
| 1 | 1286/4082 (31.5) | 701/2109 (33.2) | 585/1973 (29.7) | <0.001 | 0.146 | 0.115 |
| 2‐3 | 2103/4082 (51.5) | 1111/2109 (52.7) | 992/1973 (50.3) | |||
| 4 or more | 693/4082 (17.0) | 297/2109 (14.1) | 396/1973 (20.1) | |||
| Parity † , n/N (%) | ||||||
| 0‐1 | 1542/4080 (37.8) | 840/2107 (39.9) | 702/1973 (35.6) | <0.001 | 0.158 | 0.117 |
| 2‐3 | 2079/4080 (51.0) | 1086/2107 (51.5) | 993/1973 (50.3) | |||
| 4 or more | 459/4080 (11.3) | 181/2107 (8.6) | 278/1973 (14.1) | |||
| Antenatal visits, n/N (%) | ||||||
| 1‐3 | 1104 (27.0) | 354 (16.8) | 750 (38.0) | <0.001 | 0.458 | 0.398 |
| 4‐6 | 2147 (52.6) | 1231 (58.4) | 916 (46.4) | |||
| 7 or more | 833 (20.4) | 524 (24.8) | 309 (15.6) | |||
| HIV‐infected, n (%) | 428/4081 (10.5) | 205/2108 (9.7) | 223/1973 (11.3) | 0.100 | 0.039 | 0.032 |
| CD4 <200, n (%) | 44/393 (11.2) | 20/192 (10.4) | 24/201 (11.9) | 0.632 | ||
| Antiretroviral Therapy (ART) use among HIV‐infected, n (%) | 410/415 (98.8) | 202/202 (100) | 208/213 (97.7) | 0.028 | ||
| Non‐HIV chronic illness ‡ , n (%) | 954/3939 (24.2) | 441/2018 (21.9) | 513/1921 (26.7) | <0.001 | 0.116 | 0.125 |
| Smoked during pregnancy, n (%) | 1369/4025 (34.0) | 683/2083 (32.8) | 686/1942 (35.3) | 0.090 | 0.065 | 0.046 |
| Alcohol during pregnancy, n (%) | 376/4023 (9.3) | 193/2082 (9.3) | 183/1941 (9.4) | 0.863 | 0.007 | 0.016 |
| Trimester of vaccination, n (%) | ||||||
| First | 139/2069 (6.7) | |||||
| Second | 992/2069 (48.0) | |||||
| Third | 938/2069 (45.3) | |||||
Enrolled patients based on delivery record therefore parity reflects outcome of pregnancy under study.
Non‐HIV chronic illness included anemia (n = 246), pregnancy‐induced hypertension (n = 184), hypertension (n = 120), asthma (n = 118), diabetes (n = 76), obesity (n = 67), psychiatric disorders (n = 20), heart disease (n = 18), seizures (n = 12), and other comorbidities (n = 98).
Inverse probability of treatment weighted (IPTW) regression adjusted for maternal age, site, season of birth, campaign year, gravidity, parity, number of antenatal visits, maternal HIV status, chronic illness, smoking, and alcohol use during pregnancy.