Pregnant and lactating women who received the Moderna and Pfizer-BioNTech COVID-19 mRNA vaccines developed sufficient immunogenicity to the SARS-CoV-2 virus as well as emerging variants, according to an exploratory, descriptive cohort study published in JAMA. COVID-19 antibodies were also detected in the women’s breastmilk and their infants’ cord blood.

Investigators recruited pregnant, nonpregnant lactating, and nonpregnant, nonlactating women aged 18 to 45 years who had either received a COVID-19 vaccine or had a confirmed SARS-CoV-2 infection between December 2020 and March 2021. The investigators collected samples of blood, breast milk, and cord blood shortly after each first Moderna or Pfizer-BioNTech vaccine dose and 2 to 8 weeks after the second vaccine dose.

There were 103 women who received a COVID-19 vaccine included in the analysis; 30 were pregnant, 16 were lactating, and 57 were neither pregnant nor lactating. Among the pregnant women, 5 (17%) received their first vaccine dose during the first trimester, 15 (50%) during the second, and 10 (33%) during the third. Nine women delivered during the study and contributed infant cord blood samples. A total of 22 pregnant and 6 nonpregnant unvaccinated women who were infected with SARS-CoV-2 were included as comparators.


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Fever was reported after the second vaccine dose in 27 (52%) nonpregnant, 4 (14%) pregnant, and 7 (44%) lactating women. No severe adverse events or pregnancy or neonatal complications were reported.

Antiviral humoral immune responses, measured via IgG-binding antibody and neutralizing antibody titers, were higher for all vaccinated women compared with their prevaccination titers and compared with unvaccinated infected women. Responses of antibody-dependent monocyte, neutrophil, and complement activity were seen in vaccinated pregnant, lactating, and nonpregnant women.

Antiviral humoral immune responses were detected in paired cord and maternal blood samples of both vaccinated and unvaccinated women. The median serum IgG-binding antibody titers in maternal and cord sera were higher for vaccinated women vs unvaccinated infected women.

In breast milk samples, the median IgG-binding antibody titer was 97 in vaccinated women and 203 in unvaccinated infected women. The median IgA-binding antibodies were 25 in vaccinated women and 1940 in unvaccinated infected women. The median neutralizing antibody titers in breast milk was 75 in vaccinated women and 153 in unvaccinated infected women.

The percentage of spike-specific interferon-γ produced by CD4 T cells, CD4 central memory T cells, CD8 T cells, and CD8 central memory T cells was comparable among vaccinated pregnant, lactating, and nonpregnant women.

Serum IgG-binding antibody responses against the original SARS-CoV-2 virus and the B.1.1.7 variant were comparable among pregnant, lactating, and nonpregnant women and cord blood samples; however, responses were lower for the B.1.351 variant. Median neutralizing antibody titers were 3.5-fold lower for B.1.1.7 and 6-fold lower for B.1.351 in pregnant, lactating, and nonpregnant women vs SARS-CoV-2. However, spike-specific T-cell responses for CD4 T cells, CD4 central memory T cells, CD8 T cells, and CD8 central memory T cells were comparable for all variants in vaccinated pregnant, lactating, and nonpregnant women.

Limitations of this study include its small size, its cohort study design, and the lack of an established correlation between immunogenicity and protection against COVID-19.

“These data suggest that there may be greater cross-reactivity for functional non-neutralizing antibodies and cellular immune responses than for neutralizing antibodies against SARS-CoV-2 variants of concern,” the study authors wrote.

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

Reference

Collier AY, McMahan K, Yu J, et al. Immunogenicity of COVID-19 mRNA vaccines in pregnant and lactating women. JAMA. Published online May 13, 2021. doi:10.1001/jama.2021.7563