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Clinical Trial
. 2025 Dec;21(1):2538340.
doi: 10.1080/21645515.2025.2538340. Epub 2025 Aug 13.

Safety, immunogenicity and pregnancy outcomes in mothers and infants after vaccination with an adenovirus-vector COVID-19 vaccine during pregnancy

Gloria Aguilar  1 , Gabriela Tapia-Calle  2 , Cynthia Robinson  3 , Benoit Baron  4 , David Lowson  5 , Bassem Maximos  6 , Veronica V Rezelj  2 , Anne Marit de Groot  7 , Nicole Bet  7 , Vitalija van Paassen  4 , Mathieu Le Gars  2 , Frank Struyf  8 , Javier Ruiz-Guiñazú  9
Affiliations
Clinical Trial

Safety, immunogenicity and pregnancy outcomes in mothers and infants after vaccination with an adenovirus-vector COVID-19 vaccine during pregnancy

Gloria Aguilar et al. Hum Vaccin Immunother. 2025 Dec.

Abstract

COVID-19 during pregnancy can be associated with adverse pregnancy and infant outcomes. We assessed the safety, reactogenicity, and immunogenicity of maternal vaccination with Ad26.COV2.S COVID-19 vaccine and monitored serum and breast milk antibody levels in mothers and infants until 6 months post-delivery. This open-label Phase 2 study enrolled previously COVID-19 vaccinated or COVID-19-vaccine-naive healthy pregnant women in trimester two or three (NCT04765384). All women received a single dose of Ad26.COV2.S. Mothers and infants were followed-up for safety until 1-year post-partum and for immunogenicity, including antibodies in breast milk, until 6 months post-partum. Recruitment was stopped at 51 participants due to rapidity of roll-out of COVID-19 vaccines recommended during pregnancy. Ad26.COV2.S was well-tolerated regardless of previous COVID-19 vaccination history. All pregnancies resulted in a live infant, four were preterm. One serious adverse event of placental insufficiency Day-36 post-vaccination was considered vaccine-related by the investigator. One infant died due to complications associated with an unrelated ventricular septal defect. Ad26.COV2.S induced robust immune responses in women with different COVID-19 vaccination histories. Spike-binding antibody (SAbs) and virus neutralizing antibody (NAbs) titers at delivery tended to be higher in mothers vaccinated during trimester three. Maternal serum and cord blood were strongly correlated. 100% of infants had detectable SAbs at aged 6 months, and 70.6% had detectable NAbs, including 68.2% born to initially vaccine-naïve mothers. Maternal vaccination with an adenovirus-vector vaccine was well-tolerated and immunogenic in mothers and infants. These data could support the adoption of heterologous booster regimens during pregnancy and future adenovirus-vector vaccine development.

Keywords: Adenovirus vectors; COVID-19; SARS-CoV-2; neonates; passive antibody transfer; pregnancy; vaccine.

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Conflict of interest statement

Gabriela Tapia-Calle was an employee of Johnson & Johnson at the time of this study.

Gloria Aguilar is an employee of Johnson & Johnson and holds stock/stock options in Johnson & Johnson, LLC.

Cynthia Robinson was an employee of Johnson & Johnson at the time of this study.

Benoit Baron is an employee of Johnson & Johnson.

David Lowson is an employee of Johnson & Johnson.

Bassem Maximos has nothing to declare.

Nicole Bet was an employee of Johnson & Johnson at the time of this study.

Veronica V. Rezelj was an employee of Johnson & Johnson at the time of this study.

Vitalija van Paassen is an employee of Johnson & Johnson and holds stock or shares in Johnson & Johnson, LLC.

Marit de Groot was an employee of Johnson & Johnson at the time of this study.

Mathieu Le Gars was an employee of Johnson & Johnson at the time of this study.

Frank Struyf was an employee of Johnson & Johnson at the time of this study and holds stock/stock options in Johnson & Johnson, LLC. He holds shares in GSK as remuneration for past employment.

Javier Ruiz-Guiñazú was an employee of Johnson & Johnson and holds stock/stock options in Johnson & Johnson, LLC. He holds shares in GSK as remuneration for past employment.

Figures

Figure 1.
Figure 1.
immunogenicity in terms of A) Spike binding antibodies and B) virus neutralizing antibodies after a dose of Ad26.COV2.S during pregnancy, and C) after a booster dose post-pregnancy in initially vaccine-naïve women.
Figure 2.
Figure 2.
Immunogenicity in terms of Spike binding antibodies and virus neutralizing antibodies after a dose of Ad26.COV2.S during pregnancy by trimester of vaccination in the vaccine-naïve group.
Figure 3.
Figure 3.
Transplacental transfer of Spike binding antibodies and virus neutralizing antibodies from cord blood and post-partum blood samples from women vaccinated during pregnancy.
Figure 4.
Figure 4.
Spike binding antibodies and virus neutralizing antibodies in A) all children of women vaccinated during pregnancy; B) children of initially vaccine-naïve women by trimester at vaccination.
Figure 5.
Figure 5.
Spike-binding IgG and IgA in breast milk of women vaccinated during pregnancy.
See this image and copyright information in PMC

References

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