Maternal COVID-19 Vaccination, Infection Boosts Infant Antibody Response

This article was originally published by Contagion Live^®. This version has been lightly edited.

In the general population, hybrid immunity, from both natural infection with COVID-19 plus COVID-19 vaccination, has been shown to confer more durable immunity. This is of particular interest in vulnerable populations who are ineligible for vaccination; notably, newborns and infants younger than 6 months.

The doctor makes a revaccination of a pregnant girl against coronavirus and influenza. Prophylaxis | Image Credit: HENADZY - stock.adobe.com

Data presented at IDWeek 2023, which took place October 11-14, in Boston, Massachusetts, demonstrated that natural infection alone in pregnant mothers does not confer durable immunity in their infants, suggesting that maternal vaccination may provide better protection to these infants in the months prior to their own vaccine eligibility.¹

The study, presented by Sylvia M. LaCourse, MD, MPH, associate professor of global health and endowed chair, Medicine - Allergy and Infectious Diseases, University of Washington, included 107 pregnant participants, with a mean (SD) age of 32 years, who had experienced COVID-19 infection during pregnancy. The status of anti-Spike (anti-S) immunoglobulin G (IgG) antibodies and neutralizing antibodies was evaluated through blood sample draws at several timepoints: during pregnancy, at delivery or birth, at less than 3 months postpartum, and 3 to 6 months postpartum.

Among the participants, 27% were asymptomatic, 71% had mild to moderate COVID-19 severity, and 2% experienced severe symptoms. Two participants were hospitalized and 7 received treatment related to COVID-19 infection. At time of delivery or birth, 35% of the participants remained unvaccinated, 27% were vaccinated, and 35% had received a booster, with 3% having partial vaccination. Overall, 65% of participants had hybrid immunity (vaccination plus infection) at time of delivery or birth.

Blood tests revealed that unvaccinated mothers and their infants were less likely to have anti-S IgG+ antibodies (87% maternal, 86% infant cord blood) at birth vs those who were vaccinated (100% maternal and infant cord blood; all P ≤ .01). Results were similar for neutralizing antibodies (86% and 75%, respectively, vs vaccinated maternal: 100% for all; all P ≤ .01).

At age younger than 3 to 6 months, the percent of infants delivered to unvaccinated months with anti-S IgG+ antibodies and neutralizing antibodies dropped to 50% and 14%, respectively, compared with infants delivered to mothers with hybrid immunity, who remained at 100% across both measures (all P < .01). Overall, infants born to unvaccinated mothers with anti-S IgG+ antibodies or neutralizing antibodies displayed lower median antibody levels at birth and through their first 6 months of life compared with infants born to vaccinated mothers.

Notably, those who were vaccinated during pregnancy appeared to have more efficient transplacental transfer of anti-S IgG+ antibodies and neutralizing antibodies vs natural infection alone (anti-S IgG+ antibodies: 97% vs 73%; P <.01; neutralizing antibodies: 86% vs 54%; P = .02), again suggesting that hybrid immunity may confer a greater level of protection to infants.

These findings are in line with conclusions from similar studies, including the MOMI-VAX study² published in Vaccine earlier this year, which also demonstrated the advantage of a booster dose on antibody levels in both mothers and their cord blood. What's yet to be seen is more clear guidance on timing of vaccination/boosters that may confer the greatest amount of protection to mothers and their newborns.

References

1. LaCourse SM, Wetzler EA, Aurelio MC, et al. Maternal hybrid immunity to SARS-CoV-2 during pregnancy provides more durable infant antibody responses compared to natural infection alone. Presented at: IDWeek 2023. October 11-14, 2023; Boston, MA. Abstract 2079.
2. Munoz FM, Posavad CM, Richardson BA, et al. COVID-19 booster vaccination during pregnancy enhances maternal binding and neutralizing antibody responses and transplacental antibody transfer to the newborn. Vaccine. 2023;41(36):5296-5303. doi:10.1016/j.vaccine.2023.06.032