Impact of pregnancy on longitudinal pertussis antibody responses to Tdap vaccine in Guatemala.

Maternal immunization with tetanus, diphtheria, and acellular pertussis (Tdap) vaccine is recommended in many countries, but coverage in many low-income countries remains suboptimal. Targeted vaccination of women of child-bearing age could be a supplemental strategy to address this gap, but there are limited longitudinal immunogenicity data in this population outside of high-income countries. We compared antibody responses to Tdap between 30 non-pregnant women and 156 pregnant women enrolled in a clinical trial of maternal Tdap vaccination in Guatemala. Pre-vaccination antibody concentrations among both groups were similar for all vaccine antigens. At 2 months post-vaccination, antibody concentrations against vaccine antigens increased in both groups and were higher among non-pregnant women. By 9 months, antibody concentrations had decayed and were no longer different by study group. These findings reinforce existing recommendations for Tdap vaccination with every pregnancy. Vaccination of non-pregnant women may be considered in settings where maternal Tdap coverage is low.