Table 1.
Characteristics of the study population: infants born at Kaiser Permanente Northern California December 15, 2020—May 31, 2022
| Characteristics | Infants included in the study N = 30,311 n (%) | Infants whose mothers were vaccinated during pregnancy N = 10,893 n(%) | Infants whose mothers were not vaccinated during pregnancy N = 19,418 n (%) |
|---|---|---|---|
| Mother’s age at pregnancy onset (years), mean (std) | 31.62 (4.66) | 32.59 (4.30) | 31.08 (4.77) |
| Mother’s age category (years) | |||
| 16–<25 | 2092 (6.90) | 384 (3.53) | 1708 (8.80) |
| 25–<35 | 20,049 (66.14) | 6915 (63.48) | 13,134 (67.64) |
| 35–<50 | 8170 (26.95) | 3594 (32.99) | 4576 (23.57) |
| Mother’s race/ethnicity | |||
| Asian | 8266 (27.27) | 3682 (33.80) | 4584 (23.61) |
| Black | 1564 (5.16) | 365 (3.35) | 1199 (6.17) |
| Hispanic | 7408 (24.44) | 2146 (19.70) | 5262 (27.10) |
| Pacific Islander | 246 (0.81) | 72 (0.66) | 174 (0.90) |
| Multiracial | 108 (0.36) | 36 (0.33) | 72 (0.37) |
| Native American | 765 (2.52) | 288 (2.64) | 477 (2.46) |
| Other/unknown/multiracial | 567 (1.87) | 218 (2.00) | 349 (1.80) |
| White | 11,387 (37.57) | 4086(37.51) | 7301 (37.60) |
| Parity | |||
| 0 | 12,091 (39.89) | 4716 (43.29) | 7375 (37.98) |
| 1 | 11,189 (36.91) | 4176 (38.34) | 7013 (36.12) |
| 2 | 3925 (12.95) | 1144 (10.50) | 2781 (14.32) |
| 3 | 1213 (4.00) | 274 (2.52) | 939 (4.84) |
| 4+ | 576 (1.90) | 129 (1.18) | 447 (2.30) |
| Unknown | 1317 (4.34) | 454 (4.17) | 863 (4.44) |
| Medical comorbidity before pregnancy | |||
| Diabetes | 491 (1.62) | 217 (1.99) | 274 (1.41) |
| Hypertension | 2469 (8.15) | 889 (8.16) | 1580 (8.14) |
| Body mass index | |||
| Underweight | 659 (2.17) | 266 (2.44) | 393 (2.02) |
| Normal | 12,488 (41.20) | 4773 (43.82) | 7715 (39.73) |
| Overweight | 8845 (29.18) | 3066 (28.15) | 5779 (29.76) |
| Obese | 8212 (27.09) | 2753 (25.27) | 5459 (28.11) |
| Unknown | 107 (0.35) | 35 (0.32) | 72 (0.37) |
| Type of insurance | |||
| Subsidized (Medicare/Medicaid/other subsidized insurance) | 2008 (6.62) | 445 (4.09) | 1563 (8.05) |
| Non-subsidized | 28,303 (93.38) | 10,448 (95.91) | 17,855 (91.95) |
| Neighborhood deprivation index (quartile) | |||
| First quartile 1 (least deprived) | 7485 (24.69) | 3584 (32.90) | 3901 (20.09) |
| Second quartile | 8112 (26.76) | 2953 (27.11) | 5159 (26.57) |
| Third quartile | 7261 (23.95) | 2328 (21.37) | 4933 (25.40) |
| Fourth quartile (most deprived) | 7400 (24.41) | 2006 (18.42) | 5394 (27.78) |
| Missing | 53 (0.17) | 22 (0.20) | 31 (0.16) |
| mRNA COVID-19 vaccine doses | |||
| 0 dose | 19,418 (64.06) | 0 (0.00) | 19,418 (100) |
| 1 dose | 1138 (3.75) | 1138 (10.45) | 0 (0.00) |
| 2+ doses | 9755 (32.18) | 9755 (89.55) | 0 (0.00) |
| Gestational age at receipt of first COVID-19 vaccine dose among women receiving only one dose | |||
| First trimester | 60 (0.20) | 60 (0.55) | 0 (0.00) |
| Second trimester | 46 (0.15) | 46 (0.42) | 0 (0.00) |
| Third trimester | 1032 (3.40) | 1032 (9.47) | 0 (0.00) |
| Gestational age at receipt of second COVID-19 vaccine dose among women receiving 2+ doses | |||
| First trimester | 2082 (6.87) | 2082 (19.11) | 0 (0.00) |
| Second trimester | 3671 (12.11) | 3671 (33.70) | 0 (0.00) |
| Third trimester | 4002 (13.20) | 4002 (36.74) | 0 (0.00) |
| PCR status | |||
| Positive during first 6 months of life | 940 (3.10) | 385 (3.53) | 555 (2.86) |
| Hospitalization status | |||
| Hospitalized with positive PCR during first 6 months of life | 10 (0.03) | 1 (<0.01) | 9 (0.05) |