Reply to Heininger

To the Editor—We thank Dr Heininger for his comments and for the opportunity to discuss the implications of modifying adult booster vaccination schedules as well as the importance of pertussis vaccination among pregnant mothers. Although pertussis is relatively benign among healthy adults, it can be a severe and life- threatening disease among infants. The World Health Organization (WHO) recommends that women receive Tdap (tetanus, diphtheria, acellular pertussis) vaccination during pregnancy to increase the transfer of protective Bordetella pertussis–specific maternal antibodies to their newborns [1]. Indeed, maternal Tdap vaccination during pregnancy has been shown to reduce infant pertussis risk by ≥90% [2, 3] and is 85% more effective than postpartum Tdap vaccination of mothers at preventing infant pertussis [4].

The United States currently recommends that adults receive Td (tetanus, diphtheria) vaccination every 10 years and that at least 1 Td vaccination be substituted with Tdap in an effort to reduce pertussis transmission to infants [5]. However, it is unclear if Tdap vaccination of the general adult population is effective at combatting this infant disease since the efficacy of focused vaccination efforts on parents and close family members (referred to as “cocooning”) has been inconclusive [5]. Vaccination of mothers postpartum does not reduce the rate of pertussis among infants [6]. In a study of 53 149 infants, there was no difference in pertussis rates among infants whose parents were both vaccinated postpartum compared with those with unvaccinated parents (1.9 vs 2.2 infections per 1000 infants, respectively) [7]. Together, this indicates that maternal vaccination during pregnancy may be a more effective approach than cocooning to reduce the risk of infant pertussis.

As Dr Heininger noted, there is currently no licensed stand-alone acellular pertussis vaccine in routine use, and many countries therefore recommend Tdap at each pregnancy [8]. Our study indicates that routine/scheduled Td booster vaccinations among adults may be unnecessary for maintaining immunity against these 2 diseases [9]. However, we agree with Dr Heininger, the WHO [1] , and the Centers for Disease Control and Prevention [5] on the importance for women to receive pertussis vaccination during pregnancy to protect against infant pertussis. One caveat, however, is the potential for increased adverse reactions with repeated Tdap administrations for multiple pregnancies. In one prospective cohort study, 11.4% of pregnant women who had been vaccinated within the previous 3–4 years experienced local reactions compared with 6.0% of women who had not been vaccinated during this period of time [10]. Although it is unclear if manufacturers will find it cost-effective to produce a stand-alone acellular pertussis vaccine for pregnant women, the development of this type of vaccine could reduce vaccine-associated adverse events and is worthy of further investigation. Discontinuation of routine/decennial Td and Tdap boosters among most fully vaccinated adults may also help to reduce the total number of recent vaccinations and increase the time interval between the last booster dose and the first pregnancy as a means to further mitigate potential vaccine-related adverse events.

Notes

Financial support. This work was supported, in part, by the National Institutes of Health, Public Health Service (grant R01 AI132186 to M. K. S.) and the Oregon National Primate Research Center (grant 8P51 OD011092 to M. K. S.).

Potential conflicts of interest. The authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest.