Is the COVID-19 Vaccine Safe for Mothers Who Are Pregnant or Breastfeeding?

Updated: Jul 4

The world has been rocked by the COVID-19 pandemic, and many of us will do just about anything to hasten the return to normalcy. With the increased availability of COVID-19 vaccines, many mommas are wondering: Are they safe and effective if I’m pregnant or breastfeeding? The short answer: yes, the Pfizer and Moderna COVID-19 vaccines induce protective antibodies which are passed to baby without increased risk of side effects.


First up, let's address safety. Both vaccinations are mRNA-based. Once injected, your cells use the vaccine mRNA to make a small viral protein (not live virus) that will signal to your immune system to make antibodies against the virus. The injected mRNA is degraded within hours and will not change your cells permanently (Pardi et al., 2018). According to a preprint study (not yet peer-reviewed), vaccine mRNA is not present in breastmilk so will not be transferred from mom to baby (Golan et al., preprint). Therefore, baby's immune system will not mount a response. Further, vaccination side effects occur at the same rate in pregnant or lactating women as in the general population and are not more severe (Gray, Bordt, Atyeo, et al., 2021). According to the Phase 3 Clinical Trial reports:

  • Moderna (Baden et al., 2021): "The mRNA-1273 vaccine showed 94.1% efficacy at preventing Covid-19 illness, including severe disease. Aside from transient local and systemic reactions, no safety concerns were identified." The short-lived reactions were noted in about 50% of participants after the second shot and included fatigue, muscle pain, joint pain, and headache.

  • Pfizer/BioNTech: (Polack et al., 2020): "A two-dose regimen of BNT162b2 conferred 95% protection against Covid-19 in persons 16 years of age or older. Safety [...] was similar to that of other viral vaccines." Reported short-lived side effects included mild-to-moderate injection site pain, fatigue, and headache. After the second injection, fever was reported by "16% of younger vaccine recipients and by 11% of older recipients".

Next, let's take a look at efficacy. As noted above, both vaccinations led to ~95% protection against COVID-19 during Phase 3 Clinical Trials (Baden et al., 2021; Polack et al., 2020). For breastfeeding and pregnant mothers, a study by of 131 women (84 pregnant, 31 lactating, and 16 non-pregnant) revealed that the vaccines caused a significant rise in IgM, IgG, and IgA antibodies against SARS-CoV-2 after the administration of the first vaccine (tested at the time of the second vaccine), with a further rise in IgG after the second vaccine (tested 2-6 weeks later; Gray, Bordt, Atyeo, et al., 2021). Robust presence of protective antibodies was also observed in breastmilk and placenta at the tested time points, indicating that antibodies can be transferred to baby. Strikingly, higher levels of antibodies were observed in all vaccinated women compared to pregnant women who previously contracted COVID-19, supporting the benefits of vaccination compared to natural immunity (Gray, Bordt, Atyeo, et al., 2021).


The COVID-19 pandemic has challenged us all. These recent studies provide reassurance that getting the COVID-19 vaccine will help protect momma and baby, bringing us all closer to herd immunity.

Sources:

  • Pardi N, Hogan MJ, Porter FW, Weissman D. mRNA vaccines - a new era in vaccinology. Nat Rev Drug Discov. 2018 Apr;17(4):261-279.

  • Golan Y, Prahl M, Cassidy A, Lin CY, Ahituv N, Flaherman VJ, Gaw SL. COVID-19 mRNA vaccine is not detected in human milk. MedRvix.

  • Gray KJ, Bordt EA, Atyeo C, Deriso E, Akinwunmi B, Young N, Medina Baez A, Shook LL, Cvrk D, James K, De Guzman R, Brigida S, Diouf K, Goldfarb I, Bebell LM, Yonker LM, Fasano A, Rabi SA, Elovitz MA, Alter G, Edlow AG. COVID-19 vaccine response in pregnant and lactating women: a cohort study. Am J Obstet Gynecol. 2021 Mar 24:S0002-9378(21)00187-3.

  • Baden LR, El Sahly HM, Essink B, Kotloff K, Frey S, Novak R, Diemert D, Spector SA, Rouphael N, Creech CB, McGettigan J, Khetan S, Segall N, Solis J, Brosz A, Fierro C, Schwartz H, Neuzil K, Corey L, Gilbert P, Janes H, Follmann D, Marovich M, Mascola J, Polakowski L, Ledgerwood J, Graham BS, Bennett H, Pajon R, Knightly C, Leav B, Deng W, Zhou H, Han S, Ivarsson M, Miller J, Zaks T; COVE Study Group. Efficacy and Safety of the mRNA-1273 SARS-CoV-2 Vaccine. N Engl J Med. 2021 Feb 4;384(5):403-416.

  • Polack FP, Thomas SJ, Kitchin N, Absalon J, Gurtman A, Lockhart S, Perez JL, Pérez Marc G, Moreira ED, Zerbini C, Bailey R, Swanson KA, Roychoudhury S, Koury K, Li P, Kalina WV, Cooper D, Frenck RW Jr, Hammitt LL, Türeci Ö, Nell H, Schaefer A, Ünal S, Tresnan DB, Mather S, Dormitzer PR, Şahin U, Jansen KU, Gruber WC; C4591001 Clinical Trial Group. Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine. N Engl J Med. 2020 Dec 31;383(27):2603-2615.

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