. 2022 Jun 1;182(8):825–831. doi: 10.1001/jamainternmed.2022.2442

Table 2. Hazard Ratios of a Positive SARS-CoV-2 PCR Test in Infants Before Age 4 Months.

Characteristic	Before January 1, 2022						After January 1, 2022
	Live-born infants, No.	Follow-up time, d	COVID-19 positive test, No. (%)	Incidence rate, cases/10 000 d of follow-up	Hazard ratio (95% CI)^a		Live-born infants, No.	Follow-up time, d	COVID-19 positive test, No. (%)	Incidence rate, cases/10 000 d of follow-up	Hazard ratio (95% CI)^a
	Live-born infants, No.	Follow-up time, d	COVID-19 positive test, No. (%)	Incidence rate, cases/10 000 d of follow-up	Unadjusted	Adjusted^b	Live-born infants, No.	Follow-up time, d	COVID-19 positive test, No. (%)	Incidence rate, cases/10 000 d of follow-up	Unadjusted	Adjusted^b
Unvaccinated	9759	485967	146 (1.5)	3.0	1 [Reference]	1 [Reference]	6728	320292	350 (5.2)	10.9	1 [Reference]	1 [Reference]
Vaccinated	4696	206857	25 (0.5)	1.2	0.29 (0.19-0.44)	0.29 (0.19-0.46)	9616	546790	385 (4.0)	7.0	0.63 (0.55-0.73)	0.67 (0.57-0.79)

Abbreviation: PCR, polymerase chain reaction.

^{^a}

Infants born to women who completed their 2-dose or 3-dose vaccination series during the second or third trimesters of pregnancies were compared with infants born to unvaccinated women. Hazard ratios were obtained from a Cox proportional hazards regression model. Time was included as an interaction term for the 2 periods in the unadjusted and adjusted analyses. Number of infants included: 21 643.

^{^b}

Adjusted for maternal age, maternal parity, maternal country of birth, maternal educational attainment as of 2019, and county of residence.