Vaccinations during pregnancy are recommended because they reduce the risk of severe illness for the pregnant person and provide early protection to the infant through transferred antibodies. Pregnancy alters immune, cardiovascular, and respiratory systems in ways that can increase vulnerability to infections. Public health authorities therefore recommend specific vaccines during pregnancy to lower maternal complications and to protect newborns during their first months of life when they cannot yet complete their own vaccination series.
How vaccination protects mother and baby
Immunization stimulates the pregnant person’s immune system to produce antibodies that cross the placenta and appear in the newborn’s bloodstream. This maternal antibody transfer gives infants passive immunity against pathogens such as influenza and pertussis before their own immunizations begin. Researchers including Kathleen M. Neuzil at the University of Maryland School of Medicine have documented that maternal influenza vaccination reduces both maternal illness and influenza-related hospitalization. Kate O’Brien at Johns Hopkins Bloomberg School of Public Health and colleagues have summarized global evidence supporting maternal vaccination as an effective strategy to decrease neonatal morbidity and mortality from vaccine-preventable diseases.
Two distinct protective effects explain why vaccination is advised. First, vaccination lowers the pregnant person’s risk of infection and severe disease, which also reduces risks to the fetus such as preterm birth associated with maternal illness. Second, the antibodies produced by the parent are transferred across the placenta and via breast milk, providing temporary but meaningful protection to the infant during a high-risk period.
Safety, timing, and social considerations
Multiple large-scale safety reviews and surveillance systems have found that inactivated vaccines and certain vaccines such as Tdap for pertussis and inactivated influenza vaccines are safe in pregnancy. Saad B. Omer at Emory University Rollins School of Public Health has contributed to evidence on vaccine effectiveness and safety monitoring that underpins these recommendations. Timing matters: for pertussis-containing vaccines, administration in the late second or third trimester maximizes antibody levels transferred to the fetus, while influenza vaccination is recommended whenever influenza viruses are circulating because risk to the pregnant person can occur any trimester. Live attenuated vaccines are generally avoided during pregnancy, which is why vaccine type is an important part of clinical guidance.
Recommendations vary by country and are shaped by local disease prevalence, health-system capacity, and cultural contexts. In low-resource settings, maternal tetanus vaccination has been a major public health success for reducing neonatal tetanus deaths. In higher-income countries, the focus has expanded to include pertussis and influenza and, more recently, COVID-19 when evidence shows benefit. Equity and access are critical; communities with limited prenatal care or historical distrust of medical systems may have lower uptake, increasing disparities in both maternal and infant outcomes.
Clinicians and pregnant people should use current guidance from national public health agencies and obstetric organizations to make individualized decisions. The underlying principles are clear: maternal vaccination protects two lives at once, reduces severe disease and hospitalization, and contributes to broader community protection.