When is the Tdap (tetanus, diphtheria, and pertussis) vaccine recommended for pregnant women?

Tdap Vaccination During Pregnancy

The Tdap vaccine should be administered to all pregnant women during each pregnancy between 27 and 36 weeks gestation, preferably earlier in this window (27-30 weeks), to maximize maternal antibody transfer and provide optimal protection against pertussis for newborns. 1

Timing of Tdap Administration

Optimal Timing

• The Advisory Committee on Immunization Practices (ACIP) recommends Tdap administration between 27-36 weeks gestation for every pregnancy 1
• Evidence suggests that vaccinating earlier within this window (27-30 weeks) may maximize antibody transfer to the infant:
  • Studies show significantly higher pertussis antibody concentrations in cord blood when mothers are vaccinated at 27-30 weeks compared to later vaccination 2, 3
  • Gestational Tdap immunization between 27-30 weeks resulted in the highest avidity (strength of antibody binding) of pertussis antibodies conveyed at delivery 3

Rationale for Third Trimester Timing

• Active transport of maternal immunoglobulin G does not substantially occur before 30 weeks gestation 1
• After Tdap administration, at least 2 weeks are required to mount a maximal immune response 1
• Maternal antibodies wane quickly; women immunized during first or second trimester have low antibody levels at term 1

Effectiveness of Maternal Tdap Vaccination

• Maternal Tdap vaccination during pregnancy is 80-91% effective in preventing infant pertussis 1
• Among infants who do contract pertussis, maternal vaccination is 58% effective in preventing hospitalization 1
• Tdap vaccination at 27-36 weeks gestation is 85% more effective than postpartum vaccination at preventing pertussis in infants under 8 weeks of age 4

Special Situations

Women Due for Tetanus Booster

• If a tetanus and diphtheria booster is indicated during pregnancy (>10 years since previous Td), Tdap should be administered 1
• Optimal timing remains 27-36 weeks gestation, preferably 27-30 weeks

Wound Management

• For pregnant women requiring tetanus prophylaxis for wound management (≥5 years since previous Td booster), Tdap should be administered instead of Td 1

Incomplete Tetanus Vaccination

• For pregnant women with unknown or incomplete tetanus vaccination history:
  • Three vaccinations containing tetanus and diphtheria toxoids are recommended (0,4 weeks, and 6-12 months)
  • Tdap should replace one dose of Td, preferably between 27-36 weeks gestation 1

Implementation Challenges

Despite strong recommendations, implementation barriers exist:

• Insurance reimbursement challenges 5
• Financial concerns for practices regarding vaccine stocking 5
• Patient refusal 5

Clinical Pearls and Pitfalls

• Do not delay: If a pregnant woman presents after 36 weeks and has not received Tdap, administer it immediately rather than waiting for the postpartum period
• Every pregnancy: Tdap should be administered during every pregnancy, regardless of prior Tdap vaccination history 1
• Location matters: The vast majority (96%) of Tdap vaccinations are administered in traditional healthcare settings (obstetrician's office, primary care physician's office, or prenatal clinic) 6
• Cocooning strategy: While maternal vaccination is primary, ACIP also recommends that close contacts of infants under 12 months (parents, siblings, grandparents, childcare providers) receive Tdap if they haven't previously 1

By implementing these evidence-based recommendations for Tdap administration during pregnancy, healthcare providers can significantly reduce the risk of pertussis-related morbidity and mortality in vulnerable infants too young to be fully vaccinated themselves.