mRNA coronavirus disease (COVID-19) vaccines are highly effective at producing antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in pregnant and lactating women, a new study, the largest of its kind to date, has reported. Researchers at Massachusetts General Hospital, Brigham and Women’s Hospital, Boston, and the Ragon Institute of Massachusetts General Hospital, MIT, Boston, and Harvard, Cambridge, Massachusetts, USA, studied 131 females of reproductive age (84 pregnant, 31 lactating, and 16 nonpregnant), all of whom had received an mRNA vaccine (Pfizer/BioNTech or Moderna); all three groups showed the same levels of antibodies, and side effects were rare and comparable across all the participants.
These results are positive and encouraging for women who are pregnant or breastfeeding, who were excluded from initial COVID-19 vaccine trials. Females who are pregnant are at a greater risk of complications due to COVID-19: worse symptoms, more frequent hospitalisation, greater need for intensive care and ventilation, and increased risk of adverse pregnancy outcomes.
The team also compared vaccine-induced antibody levels against natural infection-induced levels to find that the vaccine-induced antibody levels were significantly higher than in COVID-19 infection in pregnancy. The antibodies generated from vaccinations were found to be present in the umbilical cord and breast milk, highlighting the transfer of protection from mother to baby. “We hope this study will catalyse vaccine developers to recognise the importance of studying pregnant and lactating individuals, and include them in trials,” said Galit Alter, co-senior author of the study and member of the Ragon Institute. “The potential for rational vaccine design to drive improved outcomes for mothers and infants is limitless, but developers must realise that pregnancy is a distinct immunological state, where two lives can be saved simultaneously with a powerful vaccine.”
The study also uncovered the differences in immune responses between the two mRNA vaccines: mucosal (IgA) antibodies were higher after the second Moderna dose compared to the second Pfizer dose. These findings are crucial, not only to individuals worldwide due to the fact that SARS-CoV-2 is acquired through mucosal surfaces (nose, mouth, eyes), but also to pregnant and lactating women as IgA is a key component of breastmilk.
This study indicates the ability of COVID-19 vaccines to induce immunity in this subpopulation and highlights the importance of including people who are pregnant or lactating in clinical trials.