Response

We thank Dr Warshawsky for the update on the National Advisory Committee on Immunization position on tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccination in pregnancy in response to our article.¹ Dr Warshawsky is correct that there are no data on how maternal vaccination during pregnancy affects infants’ immunologic response to the regularly scheduled acellular pertussis vaccinations at 2 months, 4 months, 6 months, and 18 months. Despite that, since 2012, the US Centers for Disease Control and Prevention Advisory Committee on Immunization Practices has recommended that women receive Tdap boosters with every pregnancy. They recommend vaccination between 27 and 36 weeks, which is the optimal time for antibody transfer.² The Advisory Committee on Immunization Practices determined that cocooning alone (vaccination of household members and close contacts) was not sufficient to reduce the number of infant pertussis cases given the severity of the disease in this age group.³

A cost-effectiveness model analysis by Terranella et al found that maternal vaccination during pregnancy would prevent more infections, hospitalizations, and infant deaths compared with the postpartum model for 2 reasons: earlier protection of the mother from pertussis, which prevents transmission to the infant; and transfer of maternal antibodies to the infant.⁴

The differences in practices and recommendations between the National Advisory Committee on Immunization and the Centers for Disease Control and Prevention illustrate the subtle differences between Canadian and American practices. That being said, both organizations agree that a pregnant woman should receive a Tdap booster in her late second to third trimester if she has not already received one in adulthood.

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