Key takeaways
Current evidence indicates that COVID-19 infection in pregnancy poses serious risks, and vaccination with the Pfizer-BioNTech (BNT162b2) vaccine is shown to be safe and effective for reducing those risks. Vaccination during pregnancy generates protective antibodies that cross the placenta and may help protect infants in the early months. Major health authorities recommend vaccination for pregnant individuals, noting known benefits that outweigh the risks, while emphasizing the importance of informed discussions with healthcare providers. This article summarizes what is known and not yet known to help readers make evidence-based decisions.
What is the Pfizer COVID-19 vaccine used in pregnancy?
The Pfizer-BioNTech COVID-19 vaccine, also known as BNT162b2, is an mRNA vaccine authorized for emergency use and later approved in many regions. It does not contain live virus and cannot cause COVID-19. Instead, it provides instructions to cells to make a harmless piece of the spike protein, triggering an immune response that offers protection against symptomatic and severe COVID-19. This same vaccine has been studied specifically in pregnant, lactating, and people planning pregnancy.
Why COVID-19 risk matters in pregnancy
Pregnancy changes immune function, breathing, and cardiovascular systems in ways that can increase the risk of severe illness from COVID-19, hospitalization, ICU admission, and need for mechanical ventilation compared with non-pregnant people. Severe outcomes can also affect the fetus through increased risk of preterm birth and related complications. Because of these pregnancy-specific risks, experts regard preventing COVID-19 as a key part of prenatal care.
Clinical evidence in pregnancy
Real-world and clinical data consistently show that vaccination in pregnancy reduces the risk of symptomatic infection, hospitalization, and severe disease. Antibodies produced after vaccination are detectable in umbilical cord blood and breast milk, suggesting potential transfer of protection to the newborn. Studies continue to monitor outcomes for both birthing people and infants, including vaccine effectiveness against emerging variants and duration of protection passed to babies.
Monitoring and pharmacology
mRNA vaccines are not thought to pose a risk to fetal development because they do not enter the cell nucleus and do not affect DNA. The lipid nanoparticles in the vaccine are designed to remain localized and are cleared from the body within days to weeks, while the mRNA degrades quickly and is not expected to cross the placenta in a biologically active form. Immunogenicity appears strong in pregnancy, with similar reactogenicity to that seen in non-pregnant people, commonly including injection site pain, fatigue, headache, and fever that resolve within a few days.
How vaccination protects infants
Passive immunity occurs when antibodies generated in the birthing person’s immune system cross the placenta during pregnancy and appear in breast milk after delivery. These antibodies can help protect newborns, who are not eligible for COVID-19 vaccines in the earliest weeks of life, during periods when their own immune defenses are still developing. This early protection may lower the chance of hospitalization due to COVID-19 in the first months of life, although the durability of this protection and effectiveness against newer variants continue to be studied.
Guidance from health authorities
Major health organizations, including the World Health Organization, U.S. Centers for Disease Control and Prevention, and the American College of Obstetricians and Gynecologists, recommend that pregnant individuals be offered access to COVID-19 vaccination and encouraged to discuss benefits and risks with their healthcare provider. Recommendations emphasize that the decision to vaccinate should be made together, taking into account individual health status, risk of exposure, and personal preferences. These guidance documents are periodically updated as new evidence emerges.
Safety monitoring and what is not yet known
Vaccine safety monitoring systems in multiple countries have not identified clear signals of uncommon but serious adverse outcomes specific to vaccination in pregnancy at rates higher than background. Ongoing studies are evaluating rare outcomes, long-term child health, and effectiveness against variants of concern. Research is also ongoing to determine the optimal timing of vaccination during pregnancy and the need for updated formulations, as well as the persistence of maternal antibodies over time.
Points not yet determined or under study
- Long-term child outcomes beyond the first year of life
- Duration and breadth of antibody transfer across the placenta and via breast milk
- Impact of vaccination timing within each trimester on pregnancy and birth outcomes
- Effectiveness against emerging variants and need for modified vaccine formulations in pregnancy
- Rare adverse events with very low incidence that require very large study populations to detect
Practical considerations for people planning pregnancy or who are pregnant
If you are trying to become pregnant, currently pregnant, or breastfeeding, consider vaccination as part of routine prenatal and postpartum care. Discuss your individual risk of exposure to COVID-19, underlying health conditions, and any concerns with your obstetrician, midwife, or primary care provider. Factors to weigh include the local level of transmission, your occupation, and access to healthcare. If you develop symptoms that suggest COVID-19, seek testing and clinical advice promptly, regardless of vaccination status.