Table 4.

Relative Vaccine Effectiveness After the Booster Dose of a Messenger RNA Coronavirus Disease 2019 Vaccine According to Pregnancy Status at the Time of Vaccination

Status at Booster Vaccination	Follow-up Time, d	Positive SARS-CoV-2 Test, No.	Unadjusted HR (95% CI)	Adjusted HR (95% CI)a
Not pregnant or postpartum	18 479	39	Ref	Ref
Postpartum	3834	8	0.98 (.46–2.10)	1.12 (.52–2.41)
Pregnant	52 820	103	0.94 (.65–1.35)	1.24 (.84–1.84)

Abbreviations: CI, confidence interval; HR, hazard ratio; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

Adjusted for age, education, income, region of birth, marital status, parity, various underlying chronic conditions, and time between dose 2 and 3 in days, in addition to pregnancy as time-varying covariate.