We thank the author for providing us an opportunity to discuss various issues involved in the recommendation of Tdap vaccination during pregnancy. 　As explained in the position paper on pertussis [1], the main objective of vaccinating pregnant woman in every pregnancy is to facilitate transplacental passage of antibodies against pertussis antigens to fetus in order to accord protection to the newborn and young infant having the highest risk of exposure, and not yet eligible to receive the first pertussis shot. Though it is desirable to have monovalent pertussis vaccine for repeated vaccinations to minimize inadvertent complications of co-administered diphtheria and tetanus antigens, non-availability of such a product limit options. Admittedly, a theoretical risk exists for severe local reactions (e.g., Arthus reactions, whole limb swelling) for pregnant women who have multiple closely spaced pregnancies. However, several studies on short intervals between receipt of tetanus and diphtheria toxoids (Td) and Tdap vaccine in healthy, non-pregnant adolescents and adults found no serious adverse events [2-4]. The committee believes the potential benefit of preventing pertussis morbidity and mortality in infants outweighs the theoretical concerns of possible severe adverse events. The safety of Tdap during pregnancy has been quite reassuring. Even during early trials of wP vaccination, up to 2-6 doses were administered in the third trimester of a single pregnancy at 1- to 2-week intervals without any serious adverse reaction to mother and to the fetus [5].

Yes, adolescents and adults including non-pregnant women also need protection against pertussis considering the short lived protection following first Tdap, but the strategy to offer repeated doses of Tdap was found to have very limited impact on the overall disease burden of pertussis. 　Further, the tactics of offering universal immunization of adolescents and adults, ‘cocooning’, and even vaccinating pregnant women immediately during post-partum period have failed to have a significant impact on incidence of pertussis amongst neonates and young infants. Repeated vaccinations with Tdap to this section would not be a cost-effective strategy considering short-lasting protection, lack of herd effect, and almost negligible impact on infantile pertussis rates. Further, it may entail a theoretical risk of accumulation of unwanted adverse effects due to co-administered diphtheria and tetanus antigens. The issue of adding second dose of Tdap was discussed in detail during one of the recent meetings of CDC Advisory Committee on Immunization Practices (ACIP), which concluded that adding second Tdap would have very limited reduction of disease burden, and would not be a cost-effective intervention.