No Evidence of Increased Adverse Outcomes for Offspring of Vaccinated Mothers

Inbal Goldshtein, PhD

There is no evidence of increased negative outcomes for offspring whose mothers were vaccinated against COVID-19.

A team, led by Inbal Goldshtein, PhD, Maccabitech Institute for Research and Innovation, Maccabi Healthcare Services, examined whether Pfizer-BioNTech COVID-19 vaccination during pregnancy was association with adverse neonatal and early infant outcomes among newborns.

Patient Concerns

Study organizers excluded pregnant women from the BNT162b2 messenger RNA (mRNA) COVID-19 vaccine (Pfizer-BioNTech) preauthorization trial, leading to a need for observational data on vaccine safety for prenatally exposed newborns. There have been multiple observational studies showing the neonatal benefits through antibody transfer across the placenta.

“Safety concerns are reported as 1 of the top reasons to decline COVID-19 vaccination during pregnancy,” the authors wrote. “The exclusion of pregnant women from the initial COVID-19 vaccine trials led to information gaps regarding maternal and fetal response to vaccination.”

At the beginning of the COVID-19 vaccine rollout, vaccine uptake was low among pregnant women. However, it did seem to surge after January 19, 2021.

The Data

In the population-based cohort study, the investigators identified all singleton live births in March through September 2021 within a large state-mandated health care organization in Israel. Each participant was followed up with until October 31, 2021.

The investigators sought main outcomes of risk ratios of preterm birth, small birth weight for gestational age, congenital malformations, all-cause hospitalizations, and infant death.

They also used stabilized inverse probability weighting to adjust for maternal age, timing of conception, parity, socioeconomic status , population subgroup, and maternal influenza immunization status.

No Evidence of Increased Rates of Negative Outcomes

Overall, there were 24,288 eligible newborns identified, 16,697 of which were exposed to maternal vaccination in utero (n = 2134 and n = 9364 in the first and second trimesters, respectively). The median follow-up following birth was 126 days among exposed newborns and 152 days among unexposed newborns. There was also no substantial differences in preterm birth rates between exposed and unexposed newborns (RR, 0.95; 95% CI, 0.83-1.10) or small birth weight for gestational age (RR, 0.97; 95% CI, 0.87-1.08).

In addition, there was no significant differences observed in the incidence of all-cause neonatal hospitalizations (RR , 0.99; 95% CI, 0.88-1.12), post neonatal hospitalizations after birth (RR , 0.95; 95% CI, 0.84-1.07), congenital anomalies (RR , 0.69; 95% CI, 0.44-1.04), or infant mortality over the study period (RR , 0.84; 95% CI, 0.43-1.72).

“This large population-based study found no evident differences between newborns of women who received BNT162b2 mRNA vaccination during pregnancy, vs those of women who were not vaccinated, and contributes to current evidence in establishing the safety of prenatal vaccine exposure to the newborns. Interpretation of study findings is limited by the observational design,” the authors wrote.

There were some limitations identified in the study, including inference regarding rare outcomes primarily focused on exposure during the second or third trimesters because the number of newborns exposed during the first trimester was underpowered to detect rare safety events at birth or after birth.

The investigators also included only live births in the cohort and did not assessed fetal safety due to potential live-born bias.

The study, “Association of BNT162b2 COVID-19 Vaccination During Pregnancy With Neonatal and Early Infant Outcomes,” was published online in JAMA Pediatrics.