The Pfizer-BioNTech and Moderna COVID-19 vaccines may offer slightly more protection during pregnancy against SARS-CoV-2, compared to the Jansen/Johnson & Johnson vaccine, suggests a study funded by the National Institutes of Health. Vaccination during the first and third trimesters appears to result in higher antibody-stimulated immune responses than vaccination in the second trimester. It also may lead to greater transfer of antibodies from maternal blood to the placenta.
Pregnant people receiving the Pfizer and Moderna vaccines had slightly higher levels of antibodies in their blood circulation and in their umbilical cord blood, compared to pregnant people who received the Johnson & Johnson vaccine. Moreover, lab tests indicated that antibodies produced in response to the Pfizer and Moderna vaccines may have been more effective at rallying other parts of the immune system against the virus than the Johnson & Johnson vaccine.
The research team was led by Andrea G. Edlow, M.D., of Massachusetts General Hospital. The study appears in Nature Communications. NIH funding was provided by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the National Heart, Lung, and Blood Institute, the National Institute of Allergy and Infectious Diseases, and the National Institute on Drug Abuse.
COVID-19 during pregnancy increases the risk of maternal and infant illness and death. Pregnant individuals were not included in the initial clinical trials of COVID-19 vaccines, resulting in a lack of information to guide vaccine-related decisions, the study authors wrote. Since these initial trials, population studies have shown that vaccination against SARS-CoV-2 during pregnancy is safe and effective against COVID-19.
Little is known, however, about the most appropriate time during pregnancy to vaccinate against the virus, about how much protection vaccination offers the fetus and newborn, and how effective existing vaccines are relative to each other.
The current study included 175 mother and infant pairs: 27 had received the Johnson & Johnson vaccine, 62 received the Moderna vaccine, and 86 received the Pfizer vaccine. The researchers analyzed samples from the participants’ blood and placental blood at delivery.
Samples from individuals vaccinated with the Moderna and Pfizer vaccines had higher levels of antibodies to the spike protein—which SARS-CoV-2 uses to bind to and infect cells—compared to samples from individuals vaccinated with the Johnson & Johnson vaccine. Antibodies generated in response to the Moderna and Pfizer vaccines marshalled stronger responses from other parts of the immune system than did the Johnson & Johnson vaccine. These responses included activation of other infection fighting white blood cells, such a neutrophils and natural killer cells, and from complement (an immune protein).
Similarly, compared to the Johnson & Johnson vaccine, the Moderna and Pfizer vaccines also induced higher levels of neutralizing antibodies—a class of antibodies that prevent viruses from entering the cell—likely to prevent infection with the Omicron variant.
Participants vaccinated in the first and third trimesters had higher antibody levels and accompanying immune responses, compared to those vaccinated in the second trimester. They also had higher levels of antibodies in their placental blood. In addition, maternal and placental antibody levels were higher for those receiving the Moderna and Pfizer vaccines than for those receiving the Johnson & Johnson vaccines.
The authors said their findings provide information that will be helpful for future studies seeking to design COVID-19 vaccines for pregnant individuals.
Atyeo, CG, et al. Maternal immune response and placental antibody transfer after COVID-19 vaccination across trimester and platforms. Nature Communications. 2022.