Effectiveness of Diphtheria and Tetanus Toxoids and Acellular Pertussis Vaccine in Children Aged 6 Months-6 Years During a Statewide Pertussis Outbreak - Alaska, May-November 2024.

Widespread use of pertussis vaccines in children has resulted in a >90% reduction in the number of annual pertussis cases in the United States. After a period of low U.S. pertussis incidence during and shortly after the COVID-19 pandemic, incidence increased in 2024. Data on the real-world effectiveness of diphtheria and tetanus toxoids and acellular pertussis vaccine (DTaP) against pertussis during this disease resurgence are limited. In response to documentation of a record high pertussis incidence in Alaska during May-November 2024, DTaP vaccine effectiveness (VE) against pertussis in Alaska children aged 6 months-6 years was evaluated. Adjusted VE was 96.2% among children who had completed the 3-dose primary DTaP series and 85.3% among those who were partially vaccinated. Compared with children who had received ≥3 DTaP doses, the odds of laboratory-confirmed pertussis were approximately 26 times as high in unvaccinated children (adjusted odds ratio [OR] = 26.1), and approximately 4 times as high in those who had received 1-2 DTaP doses (adjusted OR = 3.8). These findings reinforce the importance of following pertussis vaccination recommendations to protect for children from the disease and reduce the occurrence of pertussis outbreaks.