HealthDay News — Women receiving the COVID-19 vaccine in their third trimester of pregnancy generate a strong immune response and pass protective antibodies through umbilical cord blood to their babies, according to a research letter published online April 28 in Obstetrics & Gynecology.

Malavika Prabhu, M.D., from Weill Cornell Medicine in New York City, and colleagues studied cord blood collected at the time of birth from 122 pregnant women self-reporting receipt of one (55 women) or both (67 women) doses of a messenger RNA (mRNA)-based COVID-19 vaccine.

The researchers found that 87 pregnant women tested at birth produced an immunoglobin (Ig)G response, while 19 women produced both an IgM and IgG response. Sixteen women had no detectable antibody response but were within four weeks of vaccine dose 1. The number of women who mounted an antibody response and who conferred passive immunity to their neonates increased with the number of weeks elapsed. By four weeks after vaccination dose 1, all women and cord blood samples, except for one, had detectable IgG antibodies. For the one dyad with no transfer of antibodies to the neonate, 10 weeks passed from dose 1 and six weeks from dose 2. Five days after the first dose was the earliest detection of antibodies in women, and the earliest detection of antibodies in cord blood was at 16 days after vaccine dose 1.


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“Given the variability in antibody transfer and lack of transfer to one neonate, further studies are needed to understand the factors that influence transplacental transfer of IgG antibodies, as well as the protective nature of these antibodies,” the authors write.

One author disclosed financial ties to the pharmaceutical and medical technology industries.

Abstract/Full Text