COVID-19 Booster Vaccination During Pregnancy Elicits Robust Immunity

COVID-19 mRNA primary series vaccination during pregnancy produces robust immune responses in mothers and their newborns. Moreover, the administration of a booster dose during pregnancy significantly increases maternal and cord blood binding and neutralizing antibody (nAb) levels. These study results were published in Vaccine.

A multicenter, prospective cohort study was designed to evaluate functional immune responses among mothers and their newborns following COVID-19 vaccination. Immune responses to the ancestral COVID-19 strain and the Omicron BA.1 variant were compared between participants who received primary series vs booster vaccination during pregnancy.

The study was conducted in the United States from July 2021 to January 2022. Researchers evaluated immunoglobulin (Ig) G and receptor-binding domain (RBD) levels. They also examined SARS-CoV-2 binding and live virus and pseudovirus nAb titers at pre- and postvaccination, as well at delivery for both mothers and their newborns. Regression analyses were performed to compare differences in antibody levels at delivery between recipients of primary series vs booster vaccination, with adjustments for time since receipt of the most recent vaccine dose and prior self-reported COVID-19 infection.

A total of 240 women were included in the analysis and vaccinated during pregnancy, of whom 100 (102 newborns) received BNT162b2, 67 (68 newborns) received mRNA-1273, and 73 (75 newborns) received booster doses. Overall, the median age was 34 (range, 22-51) years, and primary series and booster vaccination was completed at a median of 17.1- and 28.6-weeks’ gestation, respectively.

Postvaccination sera were collected at a median of 18.7 (range, 1.6-33.3) weeks following primary series vaccination and 6.0 (range, 1.1-19.9) weeks following booster vaccination. Prior COVID-19 infection was self-reported by 14.4% of primary series recipients and 17.8% of booster dose recipients.

Antibodies levels measured after vaccination and at delivery were significantly higher among booster vs primary series recipients. Sera collected at delivery showed that geometric mean titers (GMTs) of anti-spike IgG antibodies were highest among booster recipients (2201 binding antibody units [BAU]/mL), followed by mRNA-1273 recipients (479 BAU/mL) and BNT162b2 recipients (236 BAU/mL). Booster vaccination also was associated with significantly higher anti-spike IgG antibodies in cord blood (GMT, 3290 BAU/mL) when compared with primary series vaccination via BNT162b2 (GMT, 369 BAU/mL) or mRNA-1273 (GMT, 792 BAU/mL).

At the time of delivery, live virus nAb titers against Omicron BA.1 were detected in 73% of booster recipients, 22% of mRNA-1273 recipients, and 9% of BNT162b2 recipients (P <.0001). Live virus nAb titers against Omicron BA.1 were also significantly higher in cord blood for booster recipients overall, with a detection rate of 88%.

Receipt of either primary series or booster vaccination during pregnancy was associated with efficient transplacental transfer (ratio ≥1.0). The median antibody transfer ratio ranged between 1.55 and 1.77 for binding IgG antibodies, 1.00 and 1.78 for live virus nAbs, and 1.79 and 2.36 for pseudovirus nAbs.

Limitations of this study include the observational design, thus the timing of vaccination during pregnancy was not predetermined and the timing of postvaccination sera collection was opportunistic.

According to the researchers “Our study supports that COVID-19 vaccination, and particularly booster doses, should be strongly recommended during pregnancy for maternal and neonatal protection.”

Disclosure: Multiple study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

This article originally appeared on Infectious Disease Advisor