As the COVID-19 vaccine rollout began in the United States in December 2020, many of us breathed a sigh of relief. The end of the pandemic seemed at last to be within sight. For those who were pregnant or breastfeeding, however, the outlook wasn’t so clear.
At issue: The initial clinical trials testing the efficacy and safety of vaccines in development excluded people who were pregnant or breastfeeding. In some countries, they were barred from receiving a COVID-19 vaccine. No such bans exist in the United States.
Weighing vaccine risks and benefits
“The message in the U.S. was, ‘Have a conversation with your physician to discuss the risks and benefits so you can make a decision,'” said Kathryn Gray, MD, PhD. Dr. Gray is an associate obstetrician in the Division of Maternal-Fetal Medicine at Brigham and Women’s Hospital.
“But in these cases we were stuck telling our patients that we didn’t have the data to make informed recommendations,” added Khady Diouf, MD, an obstetrician-gynecologist and director of the Brigham’s obstetrics and gynecology practices. “The uncertainty was unfair to women and their babies.”
Drs. Gray and Diouf are among the authors of a study that offers new insights on the efficacy of the messenger RNA (mRNA) COVID-19 vaccines from Pfizer and Moderna. Their work, along with safety data published by the Centers for Disease Control and Prevention (CDC), provides ample reason for optimism.
“Put all this data together, and we have a pretty good set of evidence for pregnant and lactating women who are considering getting vaccinated,” Dr. Diouf said.
Mass General Brigham hospitals partner on COVID-19 vaccine study
The study was a collaborative effort between the Brigham and Massachusetts General Hospital. Both hospitals are both part of the Mass General Brigham integrated health care system (previously known as Partners HealthCare). Teams from the two hospitals recruited participants and worked together closely to collect and analyze data.
A total of 131 reproductive-age pregnant, breastfeeding and nonpregnant women took part in the study. Each person received one of the two mRNA vaccines that the U.S. Food and Drug Administration had authorized for emergency use.
Drs. Gray and Diouf highlighted three key takeaways from the study:
- Pregnant and breastfeeding women were equally as likely to generate COVID-fighting antibodies as were nonpregnant women. “We now have data showing that pregnant and lactating women were able to mount an immune response to the vaccine similar to that of nonpregnant women,” Dr. Diouf said.
- Pregnant and breastfeeding women had a more powerful immune response to the vaccine than do pregnant women with prior COVID natural infection. “The vaccines are able to induce a higher antibody response than the infection does. So even if you had COVID before, you should still get a vaccine,” Dr. Gray said.
- These immunity-related benefits seem to be passed on from mother to baby via the placenta and breastmilk. “It was very promising to see vaccine-generated antibodies in the umbilical cord blood and breastmilk. This suggests some protective effect for babies,” Dr. Diouf said.
COVID-19 vaccines could become standard during pregnancy
Dr. Gray stressed that the study does not show mRNA vaccines are safe in pregnant and lactating women. However, the CDC has since published data drawn from its vaccine pregnancy registry demonstrating no increased safety risk for pregnant people or babies. While continued monitoring is needed to assess long-term outcomes, the initial signs are encouraging.
“Currently, we offer two routine vaccines during pregnancy — the influenza [flu] vaccine and the Tdap [tetanus, diphtheria and pertussis] vaccine,” Dr. Diouf concluded. “Our study, in addition to the CDC data, provides some hope that we may be able to administer the COVID-19 vaccines in pregnancy if it turns out that COVID-19 is here to stay.”