Prevalence of Pertussis Antibodies in Maternal Blood, Cord Serum, and Infants From Mothers With and Those Without Tdap Booster Vaccination During Pregnancy in Argentina.

Background: Morbidity and mortality rates for pertussis in infants are high because disease often occurs before the onset of routine immunization or in those who do not complete a primary immunization series. Pertussis immunization is recommended during pregnancy to achieve antibody levels sufficient to protect young infants. To our knowledge, no previous reports of maternal pertussis immunization results in Latin America exist in the literature.

Methods: This study compared pertussis antibody levels in newborns from mothers who received or did not receive a tetanus-diphtheria-acellular pertussis vaccination (TdapV) during pregnancy. Each mother's level of immunoglobulin G antibodies against pertussis toxin (IgG-PT) was measured with a validated, specific enzyme-linked immunosorbent assay (ELISA).

Results: Paired mother and cord serum samples were compared in 105 mothers with and 99 mothers without a TdapV. At birth, the mothers with and those without a TdapV had serum IgG-PT geometric mean concentrations (GMCs) of 35.1 and 9.8 ELISA units (EU)/mL, respectively (P < .0001); cord blood GMCs were 51.3 and 11.6 EU/mL, respectively (P < .0003); and cord blood IgG-PT levels were <5 EU/mL in 2.9% and 16.1% of the cord blood samples, respectively (P < .001). The mothers received their TdapV at a mean (± standard deviation [SD]) of 24.7 ± 4.8 weeks' gestation. Vaccination timing did not affect the IgG-PT GMC at birth. Placental antibody transference efficiencies (measured as the ratio of the cord blood GMC to the maternal GMC) were 1.46 and 1.18 for mothers with and those without a TdapV, respectively. The IgG-PT GMCs were 17.7 EU/mL in 36 infants in their first month of life and 11.6 EU/mL in 32 infants in their second month of life.

Conclusions: Women who received a TdapV during pregnancy had significantly a higher serum/cord IgG-PT concentration at birth than mothers who did not receive a TdapV. Timing of the immunization was not correlated with antibody concentrations. Infants born to immunized mothers had significantly higher antibody levels during their first 2 months of life.