(B-254) COVID-19 Vaccination During Pregnancy and Lactation and Infant Outpatient and Emergency Department Visits

Background: Concerns regarding COVID-19 vaccine safety remain a barrier to uptake, especially during pregnancy or lactation as data on infant outcomes is limited. Number of care visits may reflect overall health status in young children.

Objectives: To evaluate whether receipt of an mRNA COVID-19 vaccine during pregnancy (20 weeks gestation) or lactation is associated with increased outpatient (OP) or emergency department (ED) visits among infants.

Methods: This observational cohort study included electronic health record (EHR) and vaccine data from 4 health systems in the United States. Vaccine exposures came from EHR data and state immunization information systems. Singleton pregnancies with deliveries between December 1, 2020 and September 30, 2022 linked with infants with 1 well visit and continuous health insurance enrollment through 6 months were included. Number of infant OP and ED visits in the first 6 months of life were compared for those with and without maternal COVID-19 vaccine exposure 20 weeks gestation. Number of infant OP and ED visits were also compared within 90 days of COVID-19 vaccine exposure or matched index date for unvaccinated during lactation. We calculated visit rates, adjusted rate ratios (aRR) and 95% confidence intervals (CI) using negative binomial regression with robust variance. We used multiple imputation by chained equations for missing covariates, stabilized inverse probability of attrition weights to account for selection bias due to the continuous enrollment requirement, and stabilized inverse probability of treatment weights to account for confounding.

Results: Among 7281 singleton pregnancies ending in live birth, 2177 (29.9%) received an mRNA COVID-19 vaccine at 20 weeks gestation. In the first 6 months of life, infants with maternal vaccination at 20 weeks gestation had a rate of 6.07 OP visits and 0.18 ED while infants whose birth parent did not receive a COVID-19 vaccine at 20 weeks gestation had a rate of 5.88 OP visits and 0.24 ED visits, aRR: 1.02 (95% CI 0.99–1.05) for OP visits and aRR: 1.01; (95% CI 0.83–1.23) for ED visits. Among 8566 lactating women, 2190 (25.6%) received a COVID-19 vaccine within 90 days of delivery. In the 90 days following vaccination (or index date in unvaccinated), infants with a parent vaccinated during lactation had a rate of 2.68 OP visits and 0.07 ED visits while infants with a parent who did not receive a COVID-19 vaccine during lactation had a rate of 2.62 OP visits and 0.10 ED visits, aRR: 1.03 (95% CI 0.98–1.07) for outpatient visits, aRR: 0.98 (95% CI 0.69–1.40) for ED visits.

Conclusions: Receipt of an mRNA COVID-19 vaccine during pregnancy (20 weeks gestation) or lactation was not associated with number of OP or ED visits in infants.