New study results
Ms. Carrig was one of 131 vaccinated hospital workers in the Boston area who took part in the first study to profile the immune response in pregnant and breastfeeding women and compare it with both nonpregnant and pregnant women who had COVID-19.
The study was not designed to evaluate the safety of the vaccines or whether they prevent COVID-19 illness and hospitalizations. That is the role of the large vaccine trials, the authors said.
The participants were aged 18-45 years and received both doses of either Pfizer or Moderna vaccines during one of their trimesters. They provided blood and/or breast milk samples after each vaccine dose, 2-6 weeks after the last dose, and at delivery for the 10 who gave birth during the study.
The vaccines produced a similar strong antibody response among the pregnant/breastfeeding women and nonpregnant women. Their antibody levels were much higher than those found in the pregnant women who had COVID-19, the researchers reported on March 25, 2021, in the American Journal of Obstetrics and Gynecology.
“This is important because a lot of people tend to think once they’ve had COVID-19, they are protected from the virus. This finding suggests that the vaccines produce a stronger antibody response than the infection itself, and this might be important for long-lasting protection against COVID-19,” said Dr. Parchem.
The study also addressed whether newborns benefit from the antibodies produced by their mothers. “In the 10 women who delivered, we detected antibodies in their umbilical cords and breast milk,” says Andrea Edlow, MD, lead researcher and a maternal-fetal medicine specialist at Massachusetts General Hospital.
Newborns are particularly vulnerable to respiratory infections because they have small airways and their immune systems are underdeveloped. These infections can be lethal early in life.
“The public health strategy is to vaccinate mothers against respiratory viruses, bacteria, and parasites that neonates up to 6 months are exposed to. Influenza and pertussis (whooping cough) are two examples of vaccines that we give mothers that we know transfer [antibodies] across the umbilical cord,” said Dr. Edlow.
But this “passive transfer immunity” is different from active immunity, when the body produces its own antibody immune response, she explains.
A different study, also published in March, confirmed that antibodies were transferred from 27 vaccinated pregnant mothers to their infants when they delivered. A new finding was that the women who were vaccinated with both doses and earlier in their third semester passed on more antibodies than the women who were vaccinated later or with only one dose.
Impact of the studies
The Society for Maternal-Fetal Medicine updated its guidance on counseling pregnant and lactating patients about the COVID-19 vaccines to include Dr. Edlow’s study.
“We were struck by how much pregnant and breastfeeding women want to participate in research and to help others in the same situation make decisions. I hope this will be an example to drug companies doing research on new vaccines in the future – that they should not be left behind and can make decisions themselves whether to participate after weighing the risks and benefits,” said Dr. Edlow.
She continues to enroll more vaccinated women in her study in the Boston area, including non–health care workers who have asked to take part.
“It was worth getting vaccinated and participating in the study. I know that I have antibodies and it worked and that I passed them on to Bennett. Also, I know that all the information is available for other women who are questioning whether to get vaccinated or not,” said Ms. Carrig.
Dr. Parchem is also taking part in the CDC’s v-safe pregnancy registry, which is collecting health and safety data on vaccinated pregnant women.
Before she was vaccinated, Dr. Parchem said, “my advice was very measured because we lacked data either saying that it definitely works or showing that it was unsafe. Now that we have this data supporting the benefits, I feel more confident in recommending the vaccines.”
A version of this article first appeared on Medscape.com.