Study of 2 COVID-19 Vaccines Show Positive Safety Results With Pregnancy


Preliminary study results showed no safety concerns among pregnant women that received Pfizer-BioNTech and Moderna COVID-19 vaccines.

New evidence supports pregnant women receiving coronavirus disease 2019 (COVID-19) vaccines.

Pregnant individuals are at high risk of developing severe COVID-19, and results of a recent study suggests COVID-19 vaccines for prevention of maternal adverse outcomes and for providing protection to their newborns.1,2 According to the CDC, more than 100,000 pregnant women have received a COVID-19 vaccine, based on data from the agency’s v-safe vaccine pregnancy registry.3 There are 4711 pregnant women enrolled in the v-safe registry as of April 26, 2021.3

The Study

Preliminary study results showed no safety concerns among pregnant women that received Pfizer-BioNTech and Moderna COVID-19 vaccines.4,5 The recent study evaluated data from the “v-safe after vaccination health checker” surveillance system, the v-safe registry, and the Vaccine Adverse Event Reporting System (VAERS), from December 14, 2020-February 28, 2021, to examine the initial safety of mRNA COVID-19 vaccines in pregnant individuals.5 There were 35,691 v-safe participants ages 16-54 years who identified as pregnant.

Injection-site pain was reported more frequently among patients who were pregnant compared to patients who were not pregnant.5 However, headache, myalgia, chills, and fever were reported less in women who were pregnant. There were 3958 study participants enrolled in the v-safe pregnancy registry, and 827 had a completed pregnancy, of which 13.9% resulted in a pregnancy loss and 86.1% were live births, including 98.3% having received the first vaccine dose during the third trimester.5

Adverse neonatal outcomes included preterm birth (9.4%) and small size for gestational age (3.2%) with no deaths reported.5 These adverse neonatal outcomes are similar to studies in pregnant individuals conducted prior to the COVID-19 pandemic.5 There were 221 pregnancy-related adverse events reported to VAERS, with spontaneous abortion (46 cases) being the most common.5

The preliminary results revealed that there were no safety concerns identified, and further monitoring is needed among individuals vaccinated in their first and second trimesters.One study limitation is that v-safe and VAERS are both voluntary reporting systems, which may underestimate the number of pregnant women vaccinated or adverse events reported.5


In a White House press conference on April 23, 2021, CDC Director Rochelle Walensky, MD, MPH, discussed the positive safety findings of the study.

“As such, CDC recommends that pregnant people receive the COVID-19 vaccine. We know that this is a deeply personal decision, and I encourage people to talk to their doctors or primary care providers to determine what is best for them and for their baby,” she said.4

CBS News clarified the CDC’s recommendation on April 27, 2021: “Dr Walensky was conveying that CDC recommends pregnant people be offered the vaccine. In her remarks, she went on to say that pregnant people should consult with their health care provider when considering vaccination.”6,7

Additionally, the CDC emphasized the growing evidence regarding the safety of COVID-19 vaccines during pregnancy. Based on positive safety findings, pharmacists and other health care professionals should feel confident recommending the Pfizer-BioNTech and Moderna COVID-19 vaccines to patients who are pregnant.


  1. CDC. People with certain medical conditions. Updated March 29, 2021. Accessed April 27, 2021.
  2. Gershman J. Evidence shows maternal COVID-19 vaccination provides antibodies to newborns. Pharmacy Times. Published March 19, 2021. Accessed April 27, 2021.
  3. CDC. v-safe COVID-19 vaccine pregnancy registry. Updated April 27, 2021. Accessed April 27, 2021.
  4. The White House. Press briefing by White House COVID-19 response team and public health officials. Published April 23, 2021. Accessed April 27, 2021.
  5. Shimabukuro TT, Kim SY, Myers TR, et al. Preliminary findings of mRNA COVID-19 vaccine safety in pregnant persons. N Engl J Med. Published online April 21, 2021. doi: 10.1056/NEJMoa2104983.
  6. Smith K. CDC reiterates guidance on safety of COVID-19 vaccines for pregnant people. CBS News. Published April 27, 2021. Accessed April 27, 2021.
  7. CDC. Information about COVID-19 vaccines for people who are pregnant or breastfeeding. Updated March 18, 2021. Accessed April 27, 2021.
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