Baseline Characteristics of the Study Population before and after Propensity Score Matching, Ontario, Canada
| Characteristic . | Unmatched Cohort . | Propensity Score–Matched Cohort . | ||||
|---|---|---|---|---|---|---|
| No. (%) of Births to Tdap-Vaccinated Women, n = 12 045 . | No (%) of Births to Tdap-Unvaccinated Women, n = 613 598 . | Std Diffa . | No (%) of Births to Tdap-Vaccinated Women, n = 12 045 . | No (%) of Births to Tdap-Unvaccinated Women, n = 60 225 . | Std Diffa . | |
| Fiscal year of birth | ||||||
| 2012–2013 | 594 (4.9) | 127 010 (20.7) | 0.49 | 594 (4.9) | 2984 (5.0) | 0.00 |
| 2013–2014 | 1634 (13.6) | 124 291 (20.3) | 0.18 | 1634 (13.6) | 8481 (14.1) | 0.01 |
| 2014–2015 | 2093 (17.4) | 123 218 (20.1) | 0.07 | 2093 (17.4) | 10 620 (17.6) | 0.01 |
| 2015–2016 | 2899 (24.1) | 121 299 (19.8) | 0.10 | 2899 (24.1) | 14 538 (24.1) | 0.00 |
| 2016–2017 | 4825 (40.1) | 117 780 (19.2) | 0.47 | 4825 (40.1) | 23 602 (39.2) | 0.02 |
| Maternal age, y | ||||||
| <20 | 186 (1.5) | 14 415 (2.3) | 0.06 | 186 (1.5) | 887 (1.5) | 0.01 |
| 20–24 | 808 (6.7) | 66 293 (10.8) | 0.15 | 808 (6.7) | 4004 (6.6) | 0.00 |
| 25–29 | 3388 (28.1) | 164 953 (26.9) | 0.03 | 3388 (28.1) | 17 204 (28.6) | 0.01 |
| 30–34 | 4775 (39.6) | 224 765 (36.6) | 0.06 | 4775 (39.6) | 23 940 (39.8) | 0.00 |
| ≥35 | 2888 (24.0) | 143 172 (23.3) | 0.02 | 2888 (24.0) | 14 190 (23.6) | 0.01 |
| Parity | ||||||
| 0 (nulliparous) | 6203 (51.5) | 270 753 (44.1) | 0.15 | 6203 (51.5) | 31 009 (51.5) | 0.00 |
| ≥1 (multiparous) | 5842 (48.5) | 342 845 (55.9) | 0.15 | 5842 (48.5) | 29 216 (48.5) | 0.00 |
| Preexisting maternal medical conditionb | ||||||
| No | 11 873 (98.6) | 602 136 (98.1) | 0.03 | 11 873 (98.6) | 59 589 (98.9) | 0.03 |
| Yes | 172 (1.4) | 11 462 (1.9) | 0.03 | 172 (1.4) | 636 (1.1) | 0.03 |
| Type of preexisting maternal medical condition | ||||||
| Asthma | 1815 (15.1) | 95 998 (15.6) | 0.02 | 1815 (15.1) | 8662 (14.4) | 0.02 |
| Chronic hypertension | 43 (0.4) | 2362 (0.4) | 0.00 | 43 (0.4) | 128 (0.2) | 0.03 |
| Diabetes | 62 (0.5) | 5076 (0.8) | 0.04 | 62 (0.5) | 210 (0.3) | 0.03 |
| Heart diseasec | 49 (0.4) | 2986 (0.5) | 0.01 | 49 (0.4) | 165 (0.3) | 0.02 |
| Obstetrical complicationd | ||||||
| No | 10 486 (87.1) | 534 237 (87.1) | 0.00 | 10 486 (87.1) | 53 550 (88.9) | 0.06 |
| Yes | 1559 (12.9) | 79 361 (12.9) | 0.00 | 1559 (12.9) | 6675 (11.1) | 0.06 |
| Delivery by cesarean | ||||||
| No | 8763 (72.7) | 436 568 (71.1) | 0.04 | 8763 (72.8) | 42 552 (70.7) | 0.05 |
| Yes | 3282 (27.3) | 177 030 (28.9) | 0.04 | 3282 (27.2) | 17 673 (29.3) | 0.05 |
| Multiple birth | ||||||
| No | 11 767 (97.7) | 592 553 (96.6) | 0.07 | 11 767 (97.7) | 59 086 (98.1) | 0.03 |
| Yes | 278 (2.3) | 21 045 (3.4) | 0.07 | 278 (2.3) | 1156 (1.9) | 0.03 |
| Prenatal care indexe | ||||||
| Adequate | 6445 (53.5) | 251 492 (41.0) | 0.25 | 6445 (53.5) | 32 677 (54.3) | 0.02 |
| Inadequate | 732 (6.1) | 73 510 (12.0) | 0.21 | 732 (6.1) | 3607 (6.0) | 0 |
| Intensive | 912 (7.6) | 36 870 (6.0) | 0.06 | 912 (7.6) | 4187 (7.0) | 0.02 |
| Intermediate | 3661 (30.4) | 209 362 (34.1) | 0.08 | 3661 (30.4) | 18 369 (30.5) | 0 |
| No care | 295 (2.4) | 42 364 (6.9) | 0.21 | 295 (2.4) | 1385 (2.3) | 0.01 |
| Neighborhood median family income quintiles | ||||||
| 1 (Lowest) | 2096 (17.4) | 129 239 (21.1) | 0.09 | 2096 (17.4) | 10 585 (17.6) | 0.00 |
| 2 | 2442 (20.3) | 122 321 (19.9) | 0.01 | 2442 (20.3) | 12 497 (20.5) | 0.01 |
| 3 | 2364 (19.6) | 124 701 (20.3) | 0.02 | 2364 (19.6) | 11 726 (19.5) | 0.00 |
| 4 | 2679 (22.2) | 134 188 (21.9) | 0.01 | 2679 (22.2) | 13 375 (22.2) | 0.00 |
| 5 (Highest) | 2464 (20.5) | 103 1429 (16.8) | 0.09 | 2464 (20.5) | 12 042 (20.0) | 0.01 |
| Rural residence | ||||||
| No | 10 914 (90.6) | 550 586 (89.7) | 0.03 | 10 914 (90.6) | 54 928 (91.2) | 0.02 |
| Yes | 1131 (9.4) | 63 012 (10.3) | 0.03 | 1131 (9.4) | 5297 (8.8) | 0.02 |
| Public health unit region | ||||||
| North west | 131 (1.1) | 10 855 (1.8) | 0.06 | 131 (1.1) | 516 (0.9) | 0.02 |
| North east | 309 (2.6) | 24 124 (3.9) | 0.08 | 309 (2.6) | 1341 (2.2) | 0.02 |
| Eastern | 1966 (16.3) | 76 286 (12.4) | 0.11 | 1966 (16.3) | 9705 (16.1) | 0.01 |
| Central east | 4307 (35.8) | 185 608 (30.3) | 0.12 | 4307 (35.8) | 21 536 (35.8) | 0.00 |
| Toronto | 3503 (29.1) | 126 614 (20.6) | 0.20 | 3503 (29.1) | 17 940 (29.8) | 0.02 |
| South west | 528 (4.4) | 69 380 (11.3) | 0.26 | 528 (4.4) | 2645 (4.4) | 0.00 |
| Central west | 1301 (10.8) | 120 731 (19.7) | 0.25 | 1301 (10.8) | 6542 (10.9) | 0.00 |
| Sex | ||||||
| Female | 5858 (48.6) | 299 118 (48.7) | 0.00 | 5858 (48.6) | 29 594 (49.1) | 0.01 |
| Male | 6187 (51.4) | 314 480 (51.3) | 0.00 | 6187 (51.4) | 30 631 (50.9) | 0.01 |
| Birth wt, g | ||||||
| <1500 | 44 (0.4) | 5316 (0.9) | 0.06 | 44 (0.4) | 489 (0.8) | 0.06 |
| 1500–2499 | 545 (4.5) | 33 866 (5.5) | 0.05 | 545 (4.5) | 3058 (5.1) | 0.03 |
| 2500–3499 | 6752 (56.1) | 332 489 (54.2) | 0.04 | 6752 (56.1) | 33 876 (56.2) | 0.00 |
| ≥3500 | 4704 (39.0) | 241 927 (39.4) | 0.01 | 4704 (39.1) | 22 802 (37.9) | 0.02 |
| Gestational age at birth in wk | ||||||
| <31 | 56 (0.5) | 6134 (1.0) | 0.06 | 56 (0.5) | 557 (0.9) | 0.05 |
| 32–33 | 63 (0.5) | 5687 (0.9) | 0.05 | 63 (0.5) | 464 (0.8) | 0.03 |
| 34 | 88 (0.7) | 5990 (1.0) | 0.03 | 88 (0.7) | 503 (0.8) | 0.01 |
| 35 | 152 (1.3) | 10 020 (1.6) | 0.03 | 152 (1.3) | 888 (1.5) | 0.02 |
| 36 | 366 (3.0) | 20 119 (3.3) | 0.01 | 366 (3.0) | 1869 (3.1) | 0.00 |
| ≥37 (term) | 11 320 (94.0) | 565 648 (92.2) | 0.07 | 11 320 (94.0) | 55 944 (92.9) | 0.04 |
| Median follow-up time in person-yr (range) | 2.3 (0.0–6.0) | 3.5 (0.0–6.0) | — | 2.3 (0.0–6.0) | 2.5 (0.0–6.0) | — |
| Characteristic . | Unmatched Cohort . | Propensity Score–Matched Cohort . | ||||
|---|---|---|---|---|---|---|
| No. (%) of Births to Tdap-Vaccinated Women, n = 12 045 . | No (%) of Births to Tdap-Unvaccinated Women, n = 613 598 . | Std Diffa . | No (%) of Births to Tdap-Vaccinated Women, n = 12 045 . | No (%) of Births to Tdap-Unvaccinated Women, n = 60 225 . | Std Diffa . | |
| Fiscal year of birth | ||||||
| 2012–2013 | 594 (4.9) | 127 010 (20.7) | 0.49 | 594 (4.9) | 2984 (5.0) | 0.00 |
| 2013–2014 | 1634 (13.6) | 124 291 (20.3) | 0.18 | 1634 (13.6) | 8481 (14.1) | 0.01 |
| 2014–2015 | 2093 (17.4) | 123 218 (20.1) | 0.07 | 2093 (17.4) | 10 620 (17.6) | 0.01 |
| 2015–2016 | 2899 (24.1) | 121 299 (19.8) | 0.10 | 2899 (24.1) | 14 538 (24.1) | 0.00 |
| 2016–2017 | 4825 (40.1) | 117 780 (19.2) | 0.47 | 4825 (40.1) | 23 602 (39.2) | 0.02 |
| Maternal age, y | ||||||
| <20 | 186 (1.5) | 14 415 (2.3) | 0.06 | 186 (1.5) | 887 (1.5) | 0.01 |
| 20–24 | 808 (6.7) | 66 293 (10.8) | 0.15 | 808 (6.7) | 4004 (6.6) | 0.00 |
| 25–29 | 3388 (28.1) | 164 953 (26.9) | 0.03 | 3388 (28.1) | 17 204 (28.6) | 0.01 |
| 30–34 | 4775 (39.6) | 224 765 (36.6) | 0.06 | 4775 (39.6) | 23 940 (39.8) | 0.00 |
| ≥35 | 2888 (24.0) | 143 172 (23.3) | 0.02 | 2888 (24.0) | 14 190 (23.6) | 0.01 |
| Parity | ||||||
| 0 (nulliparous) | 6203 (51.5) | 270 753 (44.1) | 0.15 | 6203 (51.5) | 31 009 (51.5) | 0.00 |
| ≥1 (multiparous) | 5842 (48.5) | 342 845 (55.9) | 0.15 | 5842 (48.5) | 29 216 (48.5) | 0.00 |
| Preexisting maternal medical conditionb | ||||||
| No | 11 873 (98.6) | 602 136 (98.1) | 0.03 | 11 873 (98.6) | 59 589 (98.9) | 0.03 |
| Yes | 172 (1.4) | 11 462 (1.9) | 0.03 | 172 (1.4) | 636 (1.1) | 0.03 |
| Type of preexisting maternal medical condition | ||||||
| Asthma | 1815 (15.1) | 95 998 (15.6) | 0.02 | 1815 (15.1) | 8662 (14.4) | 0.02 |
| Chronic hypertension | 43 (0.4) | 2362 (0.4) | 0.00 | 43 (0.4) | 128 (0.2) | 0.03 |
| Diabetes | 62 (0.5) | 5076 (0.8) | 0.04 | 62 (0.5) | 210 (0.3) | 0.03 |
| Heart diseasec | 49 (0.4) | 2986 (0.5) | 0.01 | 49 (0.4) | 165 (0.3) | 0.02 |
| Obstetrical complicationd | ||||||
| No | 10 486 (87.1) | 534 237 (87.1) | 0.00 | 10 486 (87.1) | 53 550 (88.9) | 0.06 |
| Yes | 1559 (12.9) | 79 361 (12.9) | 0.00 | 1559 (12.9) | 6675 (11.1) | 0.06 |
| Delivery by cesarean | ||||||
| No | 8763 (72.7) | 436 568 (71.1) | 0.04 | 8763 (72.8) | 42 552 (70.7) | 0.05 |
| Yes | 3282 (27.3) | 177 030 (28.9) | 0.04 | 3282 (27.2) | 17 673 (29.3) | 0.05 |
| Multiple birth | ||||||
| No | 11 767 (97.7) | 592 553 (96.6) | 0.07 | 11 767 (97.7) | 59 086 (98.1) | 0.03 |
| Yes | 278 (2.3) | 21 045 (3.4) | 0.07 | 278 (2.3) | 1156 (1.9) | 0.03 |
| Prenatal care indexe | ||||||
| Adequate | 6445 (53.5) | 251 492 (41.0) | 0.25 | 6445 (53.5) | 32 677 (54.3) | 0.02 |
| Inadequate | 732 (6.1) | 73 510 (12.0) | 0.21 | 732 (6.1) | 3607 (6.0) | 0 |
| Intensive | 912 (7.6) | 36 870 (6.0) | 0.06 | 912 (7.6) | 4187 (7.0) | 0.02 |
| Intermediate | 3661 (30.4) | 209 362 (34.1) | 0.08 | 3661 (30.4) | 18 369 (30.5) | 0 |
| No care | 295 (2.4) | 42 364 (6.9) | 0.21 | 295 (2.4) | 1385 (2.3) | 0.01 |
| Neighborhood median family income quintiles | ||||||
| 1 (Lowest) | 2096 (17.4) | 129 239 (21.1) | 0.09 | 2096 (17.4) | 10 585 (17.6) | 0.00 |
| 2 | 2442 (20.3) | 122 321 (19.9) | 0.01 | 2442 (20.3) | 12 497 (20.5) | 0.01 |
| 3 | 2364 (19.6) | 124 701 (20.3) | 0.02 | 2364 (19.6) | 11 726 (19.5) | 0.00 |
| 4 | 2679 (22.2) | 134 188 (21.9) | 0.01 | 2679 (22.2) | 13 375 (22.2) | 0.00 |
| 5 (Highest) | 2464 (20.5) | 103 1429 (16.8) | 0.09 | 2464 (20.5) | 12 042 (20.0) | 0.01 |
| Rural residence | ||||||
| No | 10 914 (90.6) | 550 586 (89.7) | 0.03 | 10 914 (90.6) | 54 928 (91.2) | 0.02 |
| Yes | 1131 (9.4) | 63 012 (10.3) | 0.03 | 1131 (9.4) | 5297 (8.8) | 0.02 |
| Public health unit region | ||||||
| North west | 131 (1.1) | 10 855 (1.8) | 0.06 | 131 (1.1) | 516 (0.9) | 0.02 |
| North east | 309 (2.6) | 24 124 (3.9) | 0.08 | 309 (2.6) | 1341 (2.2) | 0.02 |
| Eastern | 1966 (16.3) | 76 286 (12.4) | 0.11 | 1966 (16.3) | 9705 (16.1) | 0.01 |
| Central east | 4307 (35.8) | 185 608 (30.3) | 0.12 | 4307 (35.8) | 21 536 (35.8) | 0.00 |
| Toronto | 3503 (29.1) | 126 614 (20.6) | 0.20 | 3503 (29.1) | 17 940 (29.8) | 0.02 |
| South west | 528 (4.4) | 69 380 (11.3) | 0.26 | 528 (4.4) | 2645 (4.4) | 0.00 |
| Central west | 1301 (10.8) | 120 731 (19.7) | 0.25 | 1301 (10.8) | 6542 (10.9) | 0.00 |
| Sex | ||||||
| Female | 5858 (48.6) | 299 118 (48.7) | 0.00 | 5858 (48.6) | 29 594 (49.1) | 0.01 |
| Male | 6187 (51.4) | 314 480 (51.3) | 0.00 | 6187 (51.4) | 30 631 (50.9) | 0.01 |
| Birth wt, g | ||||||
| <1500 | 44 (0.4) | 5316 (0.9) | 0.06 | 44 (0.4) | 489 (0.8) | 0.06 |
| 1500–2499 | 545 (4.5) | 33 866 (5.5) | 0.05 | 545 (4.5) | 3058 (5.1) | 0.03 |
| 2500–3499 | 6752 (56.1) | 332 489 (54.2) | 0.04 | 6752 (56.1) | 33 876 (56.2) | 0.00 |
| ≥3500 | 4704 (39.0) | 241 927 (39.4) | 0.01 | 4704 (39.1) | 22 802 (37.9) | 0.02 |
| Gestational age at birth in wk | ||||||
| <31 | 56 (0.5) | 6134 (1.0) | 0.06 | 56 (0.5) | 557 (0.9) | 0.05 |
| 32–33 | 63 (0.5) | 5687 (0.9) | 0.05 | 63 (0.5) | 464 (0.8) | 0.03 |
| 34 | 88 (0.7) | 5990 (1.0) | 0.03 | 88 (0.7) | 503 (0.8) | 0.01 |
| 35 | 152 (1.3) | 10 020 (1.6) | 0.03 | 152 (1.3) | 888 (1.5) | 0.02 |
| 36 | 366 (3.0) | 20 119 (3.3) | 0.01 | 366 (3.0) | 1869 (3.1) | 0.00 |
| ≥37 (term) | 11 320 (94.0) | 565 648 (92.2) | 0.07 | 11 320 (94.0) | 55 944 (92.9) | 0.04 |
| Median follow-up time in person-yr (range) | 2.3 (0.0–6.0) | 3.5 (0.0–6.0) | — | 2.3 (0.0–6.0) | 2.5 (0.0–6.0) | — |
Std Diff, standardized difference; —, not applicable.
Standardized difference >0.10 indicates imbalance between Tdap-vaccinated and unvaccinated subjects.
Asthma, chronic hypertension, diabetes, or heart disease.
Cardiac valvular disease, congenital heart disease, chronic congestive heart failure, hypertensive heart disease, or chronic ischemic heart disease.
Eclampsia, gestational diabetes, placenta previa, placental abruption, pre-eclampsia, or pregnancy-induced hypertension.
Adequacy of prenatal care characterized using the Revised-Graduated Prenatal Care Use Index (see Supplemental Information 1 for description).