Table 2.
Effectiveness of COVID-19 vaccination during pregnancy against infant SARS-CoV-2 infection: cohort design
| First 2 months of life | First 4 months of life | First 6 months of life | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Infant observation period by predominant SARS-CoV-2 variant, and mother’s vaccination status | Positive test N | Crude incidence ratea | Adjustedb VE (95% CI) | Positive test N | Crude incidence ratea | Adjustedb VE (95% CI) | Positive test N | Crude incidence ratea | Adjustedb VE (95% CI) |
| Delta period | |||||||||
| Unvaccinated during pregnancy | 54 | 5.47 | Reference | 118 | 5.10 | Reference | 190 | 4.78 | Reference |
| Received ≥2 doses during pregnancy | 8 | 0.75 | 84 (66,93) | 27 | 1.43 | 62 (39,77) | 37 | 1.56 | 56 (34,71) |
| Received only 1 dose during pregnancyc | 0 | 0.00 | no estimate | 0 | 0.00 | no estimate | 4 | 1.33 | 68 (12,88) |
| Omicron period | |||||||||
| Unvaccinated during pregnancy | 54 | 16.98 | Reference | 140 | 18.32 | Reference | 302 | 21.11 | Reference |
| Received ≥2 doses during pregnancy | 54 | 16.30 | 21 (−21,48) | 175 | 17.25 | 14 (−8,32) | 320 | 16.34 | 13 (−3,26) |
| Received only 1 dose during pregnancyc | 1 | 7.87 | 50 (−72,93) | 8 | 17.79 | 36 (−23,68) | 23 | 22.73 | 7 (−29,39) |
Calendar day was used as the underlying scale to ensure that infants of vaccinated and unvaccinated mothers are compared on the same calendar days.
VE vaccine effectiveness.
aRate per 100 person-years.
bAdjusted for mother’s age, race/ethnicity, neighborhood deprivation index quartile, insurance payor, KPNC facility, pre-pregnancy BMI, diabetes, hypertension, parity, and child age.
cMost one dose only vaccines were received during the third trimester.