Vaccination in Pregnancy and Postpartum

Vaccination in pregnancy, often called maternal immunization, protects the pregnant person from infections that are more severe during pregnancy and, through transfer of antibody across the placenta, protects the newborn in the vulnerable first months before infant vaccination begins. The postpartum period adds opportunities to give vaccines that were deferred and to reduce infection risk around a newborn.

Definition

Vaccination in pregnancy and postpartum is the administration of vaccines to pregnant or recently pregnant people to protect the mother and, via maternal antibody transferred before and through birth, the infant during early life.

Scope

The topic covers the dual purpose of maternal vaccination (protecting parent and infant), the central role of transplacental antibody transfer, the general distinction between non-live vaccines considered appropriate in pregnancy and live vaccines generally deferred, and the principal examples studied in this setting: influenza, pertussis, respiratory syncytial virus, and COVID-19. It is a reference overview and does not give individual schedules, timing windows, or dosing.

Core questions

• How does a vaccine given to the mother protect the infant after birth?
• Why are non-live vaccines generally considered in pregnancy while many live vaccines are deferred?
• Which infections have the strongest evidence for maternal immunization?
• What does the postpartum period add to maternal vaccination strategy?

Key concepts

• Maternal immunization
• Transplacental IgG transfer
• Passive infant protection
• Live versus non-live vaccines in pregnancy
• Postpartum and cocooning strategies
• Vaccine safety in pregnancy

Mechanisms

Maternal vaccination works through two linked mechanisms. First, it elicits maternal antibody that crosses the placenta, predominantly as IgG in the third trimester, giving the newborn passive protection during the window before active infant immunization is effective; trials of influenza and pertussis vaccination in pregnancy and of maternal RSV vaccine demonstrate reduced infant infection on this basis. Second, immunizing the mother lowers her own risk of severe infection, which is itself elevated in pregnancy for several pathogens. The general avoidance of live attenuated vaccines reflects a theoretical concern about vaccine-strain replication in the maternal-fetal unit, so non-live (inactivated, subunit, or mRNA) vaccines are the ones studied and used antenatally.

Clinical relevance

Maternal immunization is one of the clearest illustrations of how vaccinating one person protects another, and it underpins national recommendations for vaccines such as pertussis and influenza in pregnancy. This entry explains the principles and evidence for reference and education; specific products, timing, and eligibility are set by current guidelines and individual clinical assessment.

Epidemiology

Pregnant people face higher rates of severe influenza and, for the infant, pertussis and RSV cause substantial morbidity and mortality in the first months of life when direct vaccination is not yet possible. These epidemiological facts are the rationale for maternal immunization programmes, and observational and trial data have quantified reductions in infant disease following maternal pertussis, influenza, and RSV vaccination.

History

Maternal immunization moved from a narrow set of long-standing practices to a defined field over the past two decades. Influenza vaccination in pregnancy and maternal pertussis (Tdap) programmes accumulated trial and large observational evidence in the 2010s, COVID-19 vaccination in pregnancy was studied during the pandemic, and a maternal RSV vaccine to protect infants reported pivotal trial results in 2023, marking a recent expansion of the field.

Debates

Optimal timing of maternal vaccination within pregnancy

Because transplacental transfer is greatest later in pregnancy, the best gestational window to maximise infant antibody while ensuring maternal protection is an area of ongoing study and recommendation refinement.

Communicating safety to overcome hesitancy in pregnancy

Pregnant people are often cautious about any intervention, and how to convey accumulating safety evidence for vaccines given in pregnancy remains a practical challenge.

Key figures

• Shabir Madhi
• Beate Kampmann
• Gayatri Amirthalingam

Seminal works

• madhi-2014
• amirthalingam-2014
• kampmann-2023

Frequently asked questions

How can a vaccine given to a pregnant person protect the baby?

Vaccination prompts the mother to make antibodies that cross the placenta to the fetus, so the newborn starts life with borrowed (passive) protection during the months before its own vaccinations take effect.

Why are live vaccines generally not given during pregnancy?

Live attenuated vaccines contain weakened but replicating organisms, and there is a theoretical concern about that replication during pregnancy, so non-live vaccines are the ones studied and recommended antenatally.