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COVID-19 Vaccines Work Well in Pregnant Women, Protect Neonates

For good reason, pregnant women have been unsure about receiving COVID-19 vaccines. Now, pharmacists have some important information to share with them: The vaccines work as well for them as other women and appear to confer protection on their unborn child. Here is more information on the first research to look at vaccine effect in this cohort.

BOSTON – Pregnant and lactating women were excluded from initial COVID-19 vaccine trials, so it has been unclear how effective current vaccines are in protesting those women and their infants from infection or severe responses.

A new study planned for publication in the American Journal of Obstetrics and Gynecology now has determined that pregnant and lactating women elicited comparable vaccine-induced humoral immune responses to non-pregnant controls and generated higher antibody titers than those observed following SARS-CoV-2 infection in pregnancy. In addition, according to Brigham and Women’s Hospital-led researchers, vaccine-generated antibodies were present in umbilical cord blood and breastmilk after maternal vaccination.

The authors report that their study “provides the first data from a large cohort on maternal antibody generation in response to COVID-19 vaccination, compares vaccine-generated immunity to that from natural infection in pregnancy, and suggests vaccination of pregnant and lactating women can confer robust maternal and neonatal immunity.”

The goal of the research was to evaluate the immunogenicity and reactogenicity of COVID-19 mRNA vaccination in pregnant and lactating women compared to: (1) non-pregnant controls and (2) natural COVID-19 infection in pregnancy.

Enrolled in the prospective cohort study at two academic medical centers were 131 reproductive-age vaccine recipients -- 84 pregnant, 31 lactating, and 16 non-pregnant. Researchers quantified titers of SARS-CoV-2 spike and RBD IgG, IgA and IgM in sera of the participants, as well as in breastmilk for 31 of them. Measurements occurred at baseline, second vaccine dose, 2-6 weeks post second vaccine, and at delivery by Luminex. Umbilical cord sera titers also were assessed at delivery for 10 participants.

The researchers compared titers to those of 37 pregnant women 4-12 weeks from natural infection by ELISA.; they also used a pseudovirus neutralization assay to quantify neutralizing antibody titers for the women who delivered during the study period. Post-vaccination symptoms were assessed via questionnaire, and Kruskal-Wallis tests and a mixed effects model, with correction for multiple comparisons, were used to assess differences between groups, according to the report.

Results indicate that vaccine-induced antibody titers were equivalent in pregnant and lactating compared to non-pregnant women (median [IQR] 5.59 [4.68-5.89] pregnant, 5.74 [5.06-6.22] lactating, 5.62 [4.77-5.98] non-pregnant, p = 0.24). The authors advise that all titers were significantly higher than those induced by SARS-CoV-2 infection during pregnancy (p < 0.0001).

In addition, vaccine-generated antibodies were found to be present in all umbilical cord blood and breastmilk samples. Neutralizing antibody titers were lower in umbilical cord compared to maternal sera, however, although the finding did not achieve statistical significance (median [IQR] 104.7 [61.2-188.2] maternal sera, 52.3 [11.7-69.6] cord sera, p=0.05). The study also notes that the second vaccine dose (boost dose) increased SARS-CoV-2-specific IgG, but not IgA, in maternal blood and breastmilk.

The authors write that no differences were noted in reactogenicity across the groups.

“COVID-19 mRNA vaccines generated robust humoral immunity in pregnant and lactating women, with immunogenicity and reactogenicity similar to that observed in non-pregnant women,” researchers conclude. “Vaccine-induced immune responses were significantly greater than the response to natural infection. Immune transfer to neonates occurred via placenta and breastmilk.”