What do we know so far about the COVID-19 vaccines during or before pregnancy and breastfeeding?
by Health Desk | Published on December 10, 2020 – Updated on July 25, 2022 | Explainer
July 25, 2022: As of July, 2022, many studies involving hundreds of breastfeeding mothers and their children have been published. This strengthens our knowledge and certainties of how COVID-19 vaccines taken by mothers impact their infants.
No evidence has shown or suggested that COVID-19 vaccines taken by people who are breastfeeding have been harmful or posed any risk to the mother or infant. There have not been any cases of an infant dying or being severely injured due to a mother’s COVID-19 vaccination during breastfeeding in academic literature.
In addition, very few women had any trace of mRNA in their breast milk after vaccination. Trace mRNA has not shown to be associated with any risks or harms to infants. There have been some reports of discoloration of breast milk after vaccination, but this has not been shown by research to be harmful or to impact the milk quality.
Not only has research not found COVID-19 vaccinations to be harmful to mothers or their infants when breastfeeding, research also shows that antibodies from vaccination (and infection) – which help protect against a COVID-19 infection in the body – are found in the breast milk of mothers and in the babies that they’re breastfeeding. This may offer some protection against the virus to infants.
However, mothers who have been vaccinated should not assume that their breastfeeding infants have received the full benefits of vaccination. Infants should receive shots themselves when they are eligible in order to gain stronger protection against the virus.
National and international health groups recommend a COVID-19 vaccine for people who are breastfeeding due to the benefits being greater than any potential risk.
What our experts say
None of the three leading vaccine manufacturers (Pfizer, Moderna, and AstraZeneca) have reported data about the COVID-19 vaccine on knowingly pregnant or breastfeeding individuals. As a result, we have a limited understanding of how effective the three leading vaccines are for pregnant and breastfeeding people, and if there are specific risks.
Given this lack of data, some regulators and public health entities have not included pregnant people in their vaccine recommendations to the public with some specifically warning pregnant individuals against taking the vaccine. The WHO was one of these entities until Friday, January 29. Previously their guidance said that the vaccine was "currently not recommended" for pregnant women unless they are at high risk of exposure.
While their guidance, in practice, is still similar, recommending pregnant people with comorbidities or at high risk of exposure may be vaccinated in consult with doctors, they’ve directly noted that we “don’t have any specific reason to believe there will be specific risks that would outweigh the benefits of vaccination for pregnant women.” Until there is more data on COVID-19 vaccines and pregnancy, this trend of mixed guidance across different regulatory bodies and countries is likely to if and as vaccines continue to get approved.
Pregnant people who do receive a vaccine may be able to produce an immunity to the virus from the vaccine that can cross the placenta which would help keep the baby protected after birth. Regarding safety, however, when you receive an mRNA vaccine for COVID-19 you expel the mRNA particles from your body within days, so if pregnant it’s unlikely to cross the placenta and impact the baby.
The process for collecting this data will involve analyzing the impacts of the vaccines on individuals who receive a vaccination and later discover that they’re pregnant. Countries are coordinating internal reporting and monitoring systems to record and track this information.
The clinical trials had some participants enrolled who didn’t know they were pregnant at the time of vaccination, but there were not enough of those cases to have enough data for definitive conclusions. For example, in Phase 2/3 of the Pfizer and BioNTech vaccine study, 23 pregnancies were reported through November 14, 2020. Twelve were in the vaccine group and 11 in the placebo group. Two adverse events occurred in pregnancies in the placebo group, including miscarriage. These initial data do not raise concern for lack of vaccine safety in pregnancy and breastfeeding, but more data is needed to safely recommend the use of this vaccine by pregnant and breastfeeding individuals.
The U.S. FDA also recommended in June 2020 that the pharmaceutical companies developing COVID-19 vaccines first conduct developmental and reproductive toxicity (DART) studies of their vaccine before enrolling pregnant or breastfeeding people, or women not actively avoiding pregnancy, in their trials.
Pfizer and BioNTech have directly stated that they are conducting DART studies, which will provide us with more information on the safety and efficacy of their vaccine for pregnant and breastfeeding individuals.
On December 13, the American College of Obstetricians and Gynecologists released a position paper advocating for the inclusion of pregnant women in vaccine rollouts and not waiting for further data collection. While the group advocates for obtaining informed consent from pregnant and lactating women receiving the vaccine, they feel the benefits of protection outweigh the risks. The U.S. Centers for Disease Control and Prevention (CDC), the American College of Obstetricians and Gynecologists (ACOG), and the Society for Maternal-Fetal Medicine support the use of new mRNA COVID-19 vaccines in pregnant and breastfeeding individuals when they become eligible for receiving the vaccine. As of January 26, 2021, the World Health Organization also supports pregnant and breastfeeding women receiving the Moderna mRNA vaccine if they choose.
Before more data is available, it is best for pregnant and breastfeeding individuals to speak with their doctors about the best way to proceed. While it is unlikely that a doctor would recommend a pregnant or breastfeeding person get vaccinated before more data is available unless they were high risk, every risk profile is different and is worth discussing with a care provider.
Context and background
It is considered standard practice for vaccine and clinical trials to exclude pregnant and breastfeeding individuals, due to concerns that the parent and fetus may be at increased risk to what is being tested. This risk is in part due to the fact that pregnant people have different immune responses than their non-pregnant counterparts.
By excluding pregnant individuals in clinical trials, researchers are able to study the effects of a vaccine or drug on lower-risk individuals first, and once safety, efficacy, and ultimately effectiveness have been established, eventually we can test the safety, efficacy, and effectiveness on higher-risk individuals, such as people who are pregnant or breastfeeding. This practice has been increasingly criticized as exclusionary, particularly because of the fact that pregnant people are high-risk and could benefit significantly from a vaccine.
- Study to Describe the Safety, Tolerability, Immunogenicity, and Efficacy of RNA Vaccine Candidates Against COVID-19 in Healthy Adults (Pfizer)
- SARS-CoV-2 Vaccines in Pregnant Women (NIH)
- A Study to Evaluate Efficacy, Safety, and Immunogenicity of mRNA-1273 Vaccine in Adults Aged 18 Years and Older to Prevent COVID-19 (Clinicaltrials.gov)
- A Study of a Candidate COVID-19 Vaccine (COV001) (Clinicaltrials.gov)
- Medical research again leaves pregnant women waiting for a shot at a vaccine — this time for coronavirus (The Washington Post)
- Vaccines are on the way. What does that mean for pregnant people? (The Lily)
- Vaccinating Pregnant and Lactating Patients Against COVID-19 (ACOG)
- Wondering about COVID-19 vaccines if you’re pregnant or breastfeeding? (HMS)
- The Moderna COVID-19 (mRNA-1273) vaccine: what you need to know (WHO)
Used with Permission from Health Desk, a public health hub that explains emerging COVID-19 science.