Table 1.
COVID-19 vaccine series initiation after pregnancy among individuals who gave birth between May 1 and December 31, 2021, and had not yet been vaccinated by the end of pregnancya.
| Characteristic | All |
Received ≥1 dose of COVID-19 vaccine after pregnancya |
||||
|---|---|---|---|---|---|---|
| N n = 44,986 |
%b | Number vaccinated by June 30, 2022 n = 24,141 |
Incidence rate of vaccination per 1000 person-days | Unadjusted hazard ratio (95% CI) |
Adjusted hazard ratioc (95% CI) |
|
| Maternal age (years) | ||||||
| <25 | 5,419 | 12.0 | 2,436 | 2.2 | 0.69 (0.66 to 0.72) | 0.73 (0.70 to 0.77) |
| 25–29 | 12,498 | 27.8 | 6,651 | 3.0 | 0.89 (0.87 to 0.92) | 0.92 (0.89 to 0.95) |
| 30–34 | 16,229 | 36.1 | 9,173 | 3.4 | 1.00 | 1.00 |
| 35–39 | 8,696 | 19.3 | 4,835 | 3.3 | 0.97 (0.93 to 1.00) | 0.96 (0.92 to 0.99) |
| ≥40 | 2,144 | 4.8 | 1,046 | 2.6 | 0.79 (0.75 to 0.85) | 0.79 (0.74 to 0.84) |
| Month of delivery | ||||||
| May 2021 | 7,439 | 16.5 | 5,095 | 3.7 | 1.00 | 1.00 |
| June 2021 | 6,698 | 14.9 | 4,171 | 3.2 | 0.86 (0.83 to 0.90) | 0.87 (0.83 to 0.90) |
| July 2021 | 6,335 | 14.1 | 3,771 | 3.2 | 0.84 (0.80 to 0.88) | 0.84 (0.81 to 0.88) |
| August 2021 | 6,117 | 13.6 | 3,475 | 3.3 | 0.82 (0.78 to 0.85) | 0.82 (0.79 to 0.86) |
| September 2021 | 5,496 | 12.2 | 2,858 | 3.1 | 0.74 (0.71 to 0.78) | 0.75 (0.72 to 0.78) |
| October 2021 | 4,917 | 10.9 | 2,227 | 2.7 | 0.62 (0.59 to 0.65) | 0.62 (0.59 to 0.65) |
| November 2021 | 4,193 | 9.3 | 1,528 | 2.2 | 0.47 (0.45 to 0.50) | 0.48 (0.45 to 0.50) |
| December 2021 | 3,791 | 8.4 | 1,016 | 1.7 | 0.34 (0.32 to 0.36) | 0.34 (0.32 to 0.36) |
| Parity | ||||||
| 0 (nulliparous) | 18,598 | 41.3 | 10,630 | 3.4 | 1.03 (1.01 to 1.07) | 1.07 (1.04 to 1.10) |
| 1 (primiparous) | 14,780 | 32.9 | 8,273 | 3.3 | 1.00 | 1.00 |
| ≥2 (multiparous) | 11,608 | 25.8 | 5,238 | 2.3 | 0.72 (0.69 to 0.74) | 0.71 (0.69 to 0.74) |
| Multiple birth | ||||||
| No | 44,307 | 98.5 | 23,773 | 3.0 | 1.00 | 1.00 |
| Yes | 679 | 1.5 | 368 | 3.1 | 1.02 (0.92 to 1.13) | 1.01 (0.91 to 1.12) |
| Any preexisting maternal medical conditiond | ||||||
| No | 40,463 | 89.9 | 21,560 | 3.0 | 1.00 | 1.00 |
| Yes | 4,523 | 10.1 | 2,581 | 3.4 | 1.11 (1.07 to 1.16) | 1.09 (1.05 to 1.14) |
| Exclusive breastfeeding from birth to discharge from hospital or birth centere | ||||||
| No | 22,291 | 49.6 | 12,944 | 3.5 | 1.00 | 1.00 |
| Yes | 22,695 | 50.4 | 11,197 | 2.6 | 0.80 (0.78 to 0.83) | 0.81 (0.79 to 0.84) |
| Healthcare provider who caught/delivered baby | ||||||
| Midwife | 5,728 | 12.7 | 2,344 | 2.0 | 0.65 (0.62 to 0.68) | 0.67 (0.64 to 0.70) |
| Registered Nurse or CNS/NP | 392 | 0.9 | 197 | 2.7 | 0.85 (0.74 to 0.98) | 0.88 (0.77 to 1.02) |
| Family Physician | 2,579 | 5.7 | 1,271 | 2.6 | 0.83 (0.78 to 0.87) | 0.87 (0.82 to 0.92) |
| Obstetrician | 32,482 | 72.2 | 18,298 | 3.3 | 1.00 | 1.00 |
| Other | 3,618 | 8.0 | 1,968 | 3.1 | 0.95 (0.91 to 1.00) | 0.99 (0.94 to 1.04) |
| Unattended (None) | 187 | 0.4 | 63 | 1.4 | 0.49 (0.38 to 0.63) | 0.52 (0.40 to 0.66) |
| Smoked during pregnancy | ||||||
| No | 40,894 | 90.9 | 22,454 | 3.2 | 1.00 | 1.00 |
| Yes | 4,092 | 9.1 | 1,687 | 1.9 | 0.65 (0.62 to 0.68) | 0.68 (0.65 to 0.72) |
| Substance use during pregnancyf | ||||||
| No | 41,844 | 93.0 | 22,886 | 3.1 | 1.00 | 1.00 |
| Yes | 3,142 | 7.0 | 1,255 | 1.9 | 0.64 (0.60 to 0.67) | 0.67 (0.63 to 0.71) |
| Pregnancy complicationsg | ||||||
| No | 38,626 | 85.9 | 20,347 | 2.9 | 1.00 | 1.00 |
| Yes | 6,360 | 14.1 | 3,794 | 3.7 | 1.20 (1.16 to 1.24) | 1.18 (1.14 to 1.22) |
| Preterm birth | ||||||
| No (≥37 weeks) | 41,675 | 92.6 | 22,441 | 3.1 | 1.00 | 1.00 |
| Yes (<37 Weeks) | 3,311 | 7.4 | 1,700 | 2.8 | 0.93 (0.89 to 0.98) | 0.93 (0.88 to 0.98) |
| Maternal BMI (kg/m2) | ||||||
| ≥30.0 | 9,654 | 21.5 | 5,258 | 3.1 | 1.02 (0.99 to 1.05) | 1.04 (1.00 to 1.07) |
| <30.0 | 35,332 | 78.5 | 18,883 | 3.0 | 1.00 | 1.00 |
| Neighborhood median family income quintiles | ||||||
| 1 (Lowest) | 10,885 | 24.2 | 5,441 | 2.7 | 0.81 (0.78 to 0.85) | 0.79 (0.76 to 0.83) |
| 2 | 9,656 | 21.5 | 5,109 | 2.9 | 0.89 (0.86 to 0.93) | 0.88 (0.85 to 0.92) |
| 3 | 9,606 | 21.4 | 5,276 | 3.2 | 0.96 (0.92 to 1.00) | 0.94 (0.90 to 0.98) |
| 4 | 8,637 | 19.2 | 4,858 | 3.3 | 1.00 (0.96 to 1.05) | 0.99 (0.95 to 1.04) |
| 5 (Highest) | 6,202 | 13.8 | 3,457 | 3.3 | 1.00 | 1.00 |
| Rural residence | ||||||
| No | 37,663 | 83.7 | 20,917 | 3.2 | 1.00 | 1.00 |
| Yes | 7,323 | 16.3 | 3,224 | 2.2 | 0.73 (0.70 to 0.76) | 0.72 (0.69 to 0.74) |
| PHU region of residence | ||||||
| South West | 6,503 | 14.5 | 3,169 | 2.6 | 0.90 (0.86 to 0.94) | 0.97 (0.92 to 1.02) |
| Central West | 9,827 | 21.8 | 5,251 | 3.0 | 1.02 (0.98 to 1.07) | 1.03 (0.99 to 1.07) |
| Central East | 13,126 | 29.2 | 7,534 | 3.4 | 1.13 (1.08 to 1.17) | 1.09 (1.05 to 1.13) |
| Greater Toronto Area | 7,736 | 17.2 | 4,110 | 3.0 | 1.00 | 1.00 |
| Eastern | 5,210 | 11.6 | 2,733 | 2.9 | 1.00 (0.95 to 1.05) | 1.04 (0.99 to 1.09) |
| North West | 810 | 1.8 | 462 | 3.3 | 1.12 (1.01 to 1.23) | 1.25 (1.14 to 1.38) |
| North East | 1,774 | 3.9 | 882 | 2.7 | 0.91 (0.85 to 0.98) | 1.03 (0.96 to 1.12) |
| Marginalization indicesh | ||||||
| Residential instability quintile | ||||||
| 1 (least unstable) | 8,907 | 19.8 | 4,968 | 3.3 | 1.00 | 1.00 |
| 2 | 8,387 | 18.6 | 4,652 | 3.2 | 0.99 (0.95 to 1.03) | 1.03 (0.99 to 1.07) |
| 3 | 8,640 | 19.2 | 4,611 | 3.0 | 0.93 (0.90 to 0.97) | 0.98 (0.94 to 1.02) |
| 4 | 8,516 | 18.9 | 4,399 | 2.9 | 0.89 (0.85 to 0.93) | 0.96 (0.92 to 1.01) |
| 5 (most unstable) | 10,536 | 23.4 | 5,511 | 2.9 | 0.90 (0.86 to 0.93) | 1.01 (0.96 to 1.06) |
| Material deprivation quintile | ||||||
| 1 (least deprived) | 8,086 | 18.0 | 4,746 | 3.6 | 1.00 | 1.00 |
| 2 | 8,348 | 18.6 | 4,652 | 3.3 | 0.91 (0.87 to 0.95) | 0.91 (0.87 to 0.95) |
| 3 | 8,434 | 18.7 | 4,583 | 3.1 | 0.87 (0.84 to 0.91) | 0.88 (0.84 to 0.92) |
| 4 | 8,882 | 19.7 | 4,654 | 2.9 | 0.82 (0.78 to 0.85) | 0.82 (0.78 to 0.86) |
| 5 (most deprived) | 11,236 | 25.0 | 5,506 | 2.6 | 0.73 (0.70 to 0.76) | 0.74 (0.70 to 0.79) |
| Dependency quintile | ||||||
| 1 (least dependent) | 13,974 | 31.1 | 8,082 | 3.5 | 1.00 | 1.00 |
| 2 | 9,364 | 20.8 | 5,010 | 3.0 | 0.89 (0.86 to 0.92) | 0.94 (0.90 to 0.97) |
| 3 | 7,717 | 17.2 | 3,969 | 2.8 | 0.84 (0.81 to 0.87) | 0.90 (0.86 to 0.93) |
| 4 | 7,247 | 16.1 | 3,795 | 2.9 | 0.86 (0.83 to 0.90) | 0.93 (0.89 to 0.97) |
| 5 (most dependent) | 6,684 | 14.9 | 3,285 | 2.7 | 0.80 (0.77 to 0.84) | 0.89 (0.85 to 0.93) |
| Ethnic concentration quintile | ||||||
| 1 (lowest concentration) | 7,003 | 15.6 | 3,286 | 2.5 | 1.00 | 1.00 |
| 2 | 7,329 | 16.3 | 3,674 | 2.7 | 1.10 (1.05 to 1.16) | 1.04 (0.99 to 1.09) |
| 3 | 7,469 | 16.6 | 3,917 | 2.9 | 1.18 (1.12 to 1.24) | 1.08 (1.02 to 1.13) |
| 4 | 9,249 | 20.6 | 5,038 | 3.1 | 1.23 (1.18 to 1.29) | 1.11 (1.06 to 1.17) |
| 5 (highest concentration) | 13,936 | 31.0 | 8,226 | 3.5 | 1.35 (1.30 to 1.41) | 1.30 (1.24 to 1.37) |
Abbreviations: BMI, body mass index; PHU, public health unit.
aFollow-up period extended from the day of delivery until June 30, 2022.
bColumn percentages.
cModels were adjusted for maternal age at delivery, neighborhood income quintile, rural residence, and public health unit region.
dComposite of asthma, chronic hypertension, diabetes, heart disease, thyroid disease.
eExclusive breastfeeding vs. other methods of newborn feeding from birth to discharge from hospital or birth center. Other methods of feeding comprised: breast milk substitute (formula only), breast milk substitute (other), combination of breastmilk and breastmilk substitute, and unknown feeding practices.
fSelf-reported cannabis, opioid, or alcohol use during pregnancy.
gComposite of gestational hypertension, eclampsia, pre-eclampsia, gestational diabetes, and pulmonary embolism.
hOntario Marginalization Index included neighborhood-level quintiles for residential instability (family or housing instability), material deprivation (inability to attain basic material needs), dependency (receipt of income support), and ethnic concentration (geographic areas with high concentrations of recent immigrants and/or ‘visible minorities;’ see Table S1 for details.