COVID-19 Vaccines and Pregnancy

Study sheds light on most effective COVID-19 vaccines during pregnancy

A doctor prepares a pregnant person's arm for a vaccine
Image: SDI Productions/iStock/Getty Images E+ Collection

This article is part of Harvard Medical School’s continuing coverage of COVID-19.

Pregnant individuals and newborns may face elevated risks of developing more severe cases of COVID-19 following SARS-CoV-2 infection, but research suggests that COVID-19 vaccination during pregnancy can help protect both the person giving birth and the child.

A new study led by investigators at Harvard Medical School, Massachusetts General Hospital, and Brigham and Women’s Hospital and published June 28 in Nature Communications examined how different COVID-19 vaccines and the timing of vaccination during pregnancy may impact the extent of this protection.

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“Our goal was to compare maternal antibody responses and transplacental transfer of antibody to the neonate with vaccination across all three trimesters of pregnancy, and across different vaccine platforms,” said Andrea Edlow, HMS associate professor of obstetrics, gynecology and reproductive biology at Mass General.

“We hope to use this information to better counsel patients wondering about vaccination in the first versus the second or third trimester,” Edlow said.

In the study, Edlow and her colleagues characterized antibody responses to Johnson & Johnson’s adenovirus-based vaccine, as well as mRNA-based vaccines made by Moderna and Pfizer-BioNTech in 158 pregnant individuals.

The team also evaluated the transfer of protective SARS-CoV-2 antibodies via the placenta from the pregnant person to the fetus by analyzing blood from the umbilical cord and the person giving birth in 175 pairs.

The research revealed that the Johnson & Johnson vaccine induced lower-functioning SARS-CoV-2-specific antibodies than the Moderna and Pfizer-BioNTech vaccines.

The Moderna vaccine provided subtle advantages in antibody levels and function compared with the Pfizer-BioNTech vaccine.

Additionally, the mRNA-based vaccines induced higher levels and functions of antibodies against SARS-CoV-2 variants of concern, including alpha, beta, delta, and gamma.

All three vaccines also induced antibodies that demonstrated neutralizing activity against omicron.

Pregnant people vaccinated during the first and third trimesters had enhanced immune responses compared with second trimester vaccination.

SARS-CoV-2-specific antibodies were most efficiently transferred to the fetus through the placenta following vaccination during the first and second trimesters.

“These data support the initial vaccine series early in pregnancy if it has not yet been administered, with possible boosting later in pregnancy if eligible, to optimize protective antibody titers for both mother and neonate,” said Galit Alter, HMS professor of medicine, core member of the Ragon Institute of MGH, MIT and Harvard, and co-senior author of the study.

The investigators stressed the need for more research on this topic.

“Additional studies are needed to understand how to optimize maternal and neonatal immunity induced by vaccines in general during pregnancy,” said co-senior author Kathryn Gray, HMS assistant professor of obstetrics, gynecology and reproductive biology at Brigham and Women's.

Additional authors include Caroline Atyeo, Maegan Sheehan, and Alejandro Balazs of the Ragon Institute; Lydia Shook, Rose De Guzman, Madeleine Burns,Dana Cvrk, Ilona Goldfarb, Lael Yonker, and Alessio Fasano of Mass General and HMS; Sara Brigida, Stepan Demidkin, Cordelia Muir, Arantxa Medina Baez, Erin McSweeney, Ruhi Nayak, and Allison Fialkowski of Mass General; Babatunde Akinwunmi, Maya Kumar, and Chinmay Patel of Brigham and Women’s and HMS; and Michal Elovitz of the University of Pennsylvania.

The research was supported by the NIH (K08HL1469630-03; 3K08HL146963-02S1; R01A1145840-02S1; 1U19AI167899-01; 3R37AI080289-11S1; R01AI146785; U19AI42790-01; U19AI135995-02; 1U01CA260476-01; CIVIC5N93019C00052; DP2DA040254; 1R01HD100022-01; 3R01HD100022-02S2; 1K12HD103096), Mass General, the Massachusetts Consortium on Pathogen Readiness, the Gates Foundation Global Health Vaccine Accelerator Platform (OPP1146996; INV-001650), Nancy Zimmerman, the Musk Foundation, and March of Dimes (6-FY20-223).

Adapted from a Mass General news release.