Question: The number one question my wife and I are struggling with right now concerns the vaccine (Pfizer one to be specific). I should say, we are STRONG believers in vaccines writ large.  She is pregnant and due in late April. She has higher exposure risks than average people (she works in a healthcare setting) and she takes ALL the precautions.  She has an opportunity to get the Pfizer vaccine. CDC and WHO say that pregnant women can get the vaccine, but that it is a personal choice based on risk/exposure to COVID.  We know the risks of if she were to get COVID: More severe for pregnant women, and potential implications if close to delivery date.  However, we also know that none of the COVID vaccines have data regarding impact of vaccines on still developing fetuses or the longer term implications on infants/toddlers.  All that said, we do not have enough info that gives us some level of assurance about the safety of the vaccines on fetuses and their future cognitive/physical development after birth if exposed to the vaccine while in the womb… thoughts?

Answer: Thank you for sharing this background and complicated question.  It really is problematic that pregnant and lactating women were precluded from joining the Pfizer and Moderna clinical trials; we’re operating with far from complete information.  But we do know a few things that I’ll aim to synthesize herein to help you weigh the risks/benefits.  For what it’s worth, I can also tell you that if it were me, I’d put increased weight on the risks we know rather than the theoretical risks; I’d take the vaccine.  

In addition to what’s outlined below, this conversation that the Journal of the American Medical Association hosted on 2/8, is extremely informative, COVID Vaccination in Pregnant and Breastfeeding Individuals.  And these recent articles from The New Yorker and National Geographic do a nice job synthesizing the issues too.   

Risk of contracting COVID: 

1. Risk of Infection?: We do not know whether pregnancy status is related to infection risk. 
2. Risk of Severe Illness?: We do know that pregnancy status is associated with increased disease severity, with respiratory illness requiring hospitalization in 5% – 6% of pregnant women.  Furthermore, CDC’s analysis of national surveillance data of ~400,000 women with symptomatic COVID-19 found that pregnant women were 3x more likely to be admitted to intensive care, 2.9x more likely to need mechanical ventilation, and 1.7x more likely to die as compared with non-pregnant women. We also know that COVID presents increased risk to the fetus. 
3. Risk of Adverse Birth Outcomes?: There seems to be increased risk of pre-term birth among mothers who contract COVID.  As synthesized in a recent article published in JAMA, “In studies of hospitalized pregnant women with COVID-19, which have included between 240 and 427 infected women, the risk for preterm delivery (both iatrogenic and spontaneous) has ranged from 10% to 25%, with rates as high as 60% among women with critical illness.”  There may also be an increased risk of stillbirth, though the data are not conclusive on that point. 
4. Risk of Vertical Transmission: Vertical transmission may occur and appears more likely among asymptomatic mothers, though vertical transmission is rare, especially as compared with other diseases. 

Risk of vaccination:

1. Risk to Pregnancy?: There is no risk of acquiring the disease from the mRNA vaccine.  Additionally, as Dr. Fauci stated earlier this month, “We had a lot of pregnant women vaccinated [over 10,000]. The FDA followed them and will continue to follow them.. Even though we don’t have good data on it, the data that we’re collecting on it so far has no red flags.”  Other vaccines given to pregnant women, including influenza and pertussis, have proven safe and effective. 
2. Risk to Fetus?: As the American College of Gynecology and Obstetrics (ACOG) synthesized, animal studies of the Pfizer and Moderna vaccines indicate there are “no direct or indirect harmful effects with respect to pregnancy, embryo/fetal development, parturition or post-natal development.” One potential risk of vaccination is the potential side effect of high fever.  High fever in early pregnancy has been linked to neural tube defects among women who are not ingesting at least 400g of folic acid/day.        
3. Risk to Infant/Child?: There is little in the way of plausible theoretical risks to the infant/child.  The Academy of Breastfeeding Medicine recently issued a statement concerning vaccination and breastfeeding, stating “While there is little plausible risk for the child, there is a biologically plausible benefit. Antibodies and T-cells stimulated by the vaccine may passively transfer into milk.” The Academy further addressed mRNA lipid nanoparticles that encode the ribosome instructions, stating ”  it is unlikely that the vaccine lipid would enter the bloodstream and reach breast tissue. If it does, it is even less likely that either the intact nanoparticle or mRNA transfer into milk. In the unlikely event that mRNA is present in milk, it would be expected to be digested by the child and would be unlikely to have any biological effects.” Turning to other vaccines, we have strong data indicating that influenza vaccination in pregnancy can reduce the risk of low birth weight by 15% and infant influenza illness by 30%.  And pertussis vaccine during the 3rd trimester has been proven to reduce the risk of infant pertussis illness by 85% thanks to antibody transfer in utero.