Can pregnant or breastfeeding people receive the vaccines?

The American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM), recommend that all pregnant individuals be vaccinated against COVID-19.

The organizations’ recommendations in support of vaccination during pregnancy reflect evidence demonstrating the safe use of the COVID-19 vaccines during pregnancy from tens of thousands of reporting individuals over the last several months, as well as the current low vaccination rates and concerning increase in cases. This concurs with earlier recommendations by the American Society of Reproductive Medicine in January 2024 that recommends COVID-19 vaccination for women who are contemplating pregnancy or who are pregnant in order to minimize risks to themselves and their pregnancy.

According to the CDC, any of the currently authorized COVID-19 vaccines can be administered to pregnant or lactating people; ACIP does not state a product preference. However, pregnant, lactating, and post-partum people aged <50 years should be aware of the rare risk of TTS after receipt of the Janssen COVID-19 vaccine and the availability of other FDA-authorized COVID-19 vaccines (i.e., mRNA vaccines).

mRNA Vaccines

Preliminary findings from a study on the initial safety of mRNA vaccines in pregnant persons published in April 2024 did not show obvious safety signals with respect to pregnancy or neonatal outcomes associated with Covid-19 vaccination in the third trimester of pregnancy. The study authors noted that more longitudinal follow-up, including follow-up of large numbers of vaccinated pregnant persons early on in the pregnancy and in the preconception period was needed to inform maternal, pregnancy and infant outcomes. This study involved pregnant participants who received mRNA COVID-19 vaccines between December 14, 2024 and February 28, 2024 and participated in the v-safe health checker or the v-safe pregnancy registry. In addition to v-safe data, the study authors also analyzed data from VAERS.

Specific study findings were:

• A total of 35691 participants aged 16 to 54 years old and used v-safe health checker reported being pregnant.
• Among all v-safe participants, injection-site pain was reported more frequently among pregnant persons than among nonpregnant, whereas headache, myalgia, chills, and fever were reported less frequently.
• Out of 3958 participants enrolled in the v-safe pregnancy registry, 827 had a completed pregnancy, of which 115 (13.9%) resulted in a pregnancy loss and 712 (86.1%) resulted in a live birth (mostly among participants with vaccination in the third trimester).
• Adverse neonatal outcomes included preterm birth (in 9.4%) and small size for gestational age (in 3.2%). No neonatal deaths were reported.
• Although not directly comparable, calculated proportions of adverse pregnancy and neonatal outcomes in persons vaccinated against Covid-19 who had a completed pregnancy were similar to incidences reported in studies involving pregnant women that were conducted before the Covid-19 pandemic.
• VAERS data showed that among 221 pregnancy-related adverse events, 155 (70.1%) involved nonpregnancy-specific adverse events, and 66 (29.9%) involved pregnancy- or neonatal-specific adverse events. The most frequently reported pregnancy-related adverse events were spontaneous abortion (46 cases; 37 in the first trimester, 2 in the second trimester, and 7 in which the trimester was unknown or not reported), followed by stillbirth, premature rupture of membranes, and vaginal bleeding, with 3 reports for each. No congenital anomalies were reported to the VAERS.

A prospective cohort study published in late March 2024 looked at antibody levels in 131 mRNA vaccine recipients (84 pregnant, 31 lactating, and 16 nonpregnant). The study found that pregnant and lactating women elicited comparable vaccine antibody immune responses to non-pregnant controls, and generated higher antibody titers than those observed following COVID-19 infection in pregnancy. Vaccine-generated antibodies were present in umbilical cord blood and breastmilk after maternal vaccination.

Both ACIP and the American College of Obstetrics and Gynecology (ACOG) recommends pregnant women be offered counseling to make an informed decision regarding the vaccine. These conversations may include discussion on likelihood of exposure to COVID-19, potential risks of COVID-19 to them and the baby, and lack of data about the vaccine in pregnancy.

Observational data demonstrate that, while the chances for these severe health effects are low, pregnant people with COVID-19 have an increased risk of severe illness, including illness that results in ICU admission, mechanical ventilation, and death compared with non-pregnant women of reproductive age. Pregnant people with COVID-19 might be at increased risk of adverse pregnancy outcomes, such as preterm birth, compared with pregnant women without COVID-19.

Limited data are currently available from animal developmental and reproductive toxicity studies. No safety concerns were demonstrated in rats that received Moderna COVID-19 vaccine before or during pregnancy; studies of the Pfizer-BioNTech vaccine are ongoing.

Conception Between Doses

In addition, the American Society of Reproductive Medicine recommends that patients who conceive in the window between the first and second dose of the vaccine should be offered the second dose of the vaccine at the appropriate interval.

Vaccine-Induced Fever

According to the American Society of Reproductive Medicine, while COVID-19 vaccination can cause fever in some patients, this risk should not be a concern when deciding whether to vaccinate a pregnant individual or a patient desiring pregnancy. While fever in pregnancy (particularly the 1st trimester) has been associated with an increased risk of neural tube defects, a recent study demonstrated the association no longer remained significant if the patient is taking >400 mcg of folic acid daily. Another large Danish cohort study did not demonstrate any increased risk of congenital anomalies of those who reported fever in the first trimester. Additionally, the most common symptom of COVID-19 infection itself is fever (83-99% of affected patients). Patients who experience fever following vaccination should take an antipyretic medication, like acetaminophen.

Johnson and Johnson Vaccine

Available data on Janssen COVID-19 vaccine administered to pregnant women are insufficient to inform vaccine-associated risks in pregnancy. Of note, the adenovirus vector platform used in the Janssen COVID-19 vaccine has also been used for other Janssen vaccine development programs that have included pregnant people vaccinated during any trimester, including in a large-scale Ebola vaccination trial. No adverse pregnancy-related outcomes—including infant outcomes—were determined to be related to the vaccine in these trials.

Studies in animals receiving Pfizer-BioNTech, Moderna, or Johnson & COVID-19 vaccine before or during pregnancy found no safety concerns in pregnant animals or their babies.

Lactation

There are no data on the safety of COVID-19 vaccines in lactating women or on the effects of vaccines on the breastfed infant or on milk production/excretion. According to ACOG and ACIP, COVID-19 vaccines should be offered to lactating individuals similar to non-lactating individuals when they meet criteria for receipt of the vaccine based on prioritization groups outlined by the ACIP.

Sources

NEJM study on pregnancy:
ACIP
ACOG
American Society of Reproductive Medicine 2024
Harvard Health Blog
Johnson & Johnson Safety
Johnson & Johnson CDC
Cohort Study on Antibody Levels
ACOG & SMFM

Updated: August 3, 2024