Table 2:
Risk of breakthrough or incident and severe COVID-19 infections among pregnant people (Cohort 1) by vaccination status and variant predominant periods in N3C Cohort, December 10, 2020- June 7, 2022
| Pre-Delta variant dominant period | Delta variant dominant period | Omicron variant dominant period | ||||
|---|---|---|---|---|---|---|
| Events/100 women- months (95% CI) |
Adjusted Model (M3) HR (95% CI)3 |
Events/100 women- months (95% CI) |
Adjusted Model (M3) HR (95% CI)3 |
Events/100 women- months (95% CI) |
Adjusted Model (M3) HR (95% CI)3 |
|
| Breakthrough or incident COVID-19 infection | ||||||
| Initial vaccinations | ||||||
| Unvaccinated pregnant people | 0.36 (0.22, 0.5) | Ref. | 1.36 (1.08, 1.63) | Ref. | 4.16 (3.59, 4.74) | Ref. |
| Vaccinated pregnant people with initial vaccinations during pregnancy | 0.12 (0, 0.42) | 0.36 (0.25, 0.51) | 0.91 (0.31, 1.51) | 0.77 (0.62, 0.96) | 3.7 (2.44, 4.96) | 0.88 (0.73, 1.07) |
| Vaccinated pregnant people with initial vaccinations before pregnancy | - | 0.07(0.04, 0.14) | 0.63 (0.16, 1.1) | 0.60 (0.53, 0.68) | 2.82 (1.79, 3.84) | 1.05 (0.95, 1.16) |
| Booster vaccinations | ||||||
| Unvaccinated pregnant people | 4.16 (3.59, 4.74) | Ref. | ||||
| Vaccinated pregnant people with booster vaccination during pregnancy | 2.55 (1.05, 6.01) | 0.52 (0.47, 0.58) | ||||
| Vaccinated pregnant people with booster vaccination before pregnancy | 3.21 (1.57, 4.85) | 0.52 (0.41, 0.64) | ||||
| Vaccinated pregnant people with initial vaccinations during pregnancya | 3.96 (0.99, 6.53) | Ref. | ||||
| Vaccinated pregnant people with booster vaccination during pregnancy | 2.55 (1.05, 6.01) | 0.64 (0.58, 0.71) | ||||
| Severe COVID-19 infection | ||||||
| Initial vaccinations | ||||||
| Unvaccinated pregnant people | 0.15 (0.06, 0.23) | Ref. | 0.37 (0.2, 0.54) | Ref. | ||
| Vaccinated pregnant people with initial vaccinations during pregnancy | 0.08 (0, 0.26) | 0.65 (0.45, 0.90) | 0.29 (0, 0.64) | 0.79 (0.51, 1.21) | ||
| Vaccinated pregnant people with initial vaccinations before pregnancy | 0.03 (0, 0.12) | 0.24(0.15, 0.39) | 0.12 (0, 0.32) | 0.39 (0.27, 0.56) | ||
| Booster vaccinations | ||||||
| Unvaccinated pregnant people | 0.45 (0.23, 0.53) | Ref | ||||
| Vaccinated pregnant people with booster vaccinations during pregnancy | 0.14 (0, 0.58) | 0.35 (0.22, 0.54) | ||||
| Vaccinated pregnant people with full initial vaccinations during pregnancya | 0.43 (0, 1.36) | Ref | ||||
| Vaccinated pregnant people with booster vaccination during pregnancy | 0.14 (0, 0.58) | 0.35 (0.24, 0.50) | ||||
Abbreviations: N3C=National COVID Cohort Collaborative; HR= hazard ratio; CI= confidence interval; Ref= reference; CCI= Charlson comorbidity index.
Model results were generated from Cox proportional hazard model with data partner site level clustered standard error stratified by pandemic variant periods.
Models were adjusted for sociodemographic variables such as age, race/ethnicity, region, clinical covariates such as comorbidities, CCI and prior COVID-19 positivity. Full model result was presented in supplementary table 2.
The number of people with records during variants periods is described in supplementary table 6.
Numbers in a category with number < 20 must be obfuscated to comply with the small number reporting rule for N3C.
We used initial vaccination date plus 90 days as the start follow up time for vaccinated pregnant people with initial vaccinations during pregnancy to compare with those who had booster vaccinations during their pregnancy. We excluded those with COVID-19 incidence/severe infections during the 90 days.