Vaccine Timeliness: A Cost Analysis of the Potential Implications of Delayed Pertussis Vaccination in the US

Background: Pertussis infection remains an important public health problem, particularly in infants. Despite high coverage, pertussis vaccination delays can leave infants at a vulnerable age with less protection than anticipated. Methods: Current diphtheria-tetanus-pertussis (DTaP) vaccination timeliness for the first 3 doses in the US was estimated using National Immunization Survey data. A Markov model estimated the potential impact on outcomes and costs of a hypothetical situation of vaccination at exactly 60, 120 and 180 days, compared with current timeliness. Incidence and unit cost data came from published sources. Age-specific incidence (for month of life) of pertussis and the associated probabilities of hospitalization and death for the US, during 2000-2007, were taken from a recently published US DTaP vaccination cost-effectiveness study. The cost analysis was conducted from the healthcare system's perspective over a 1-year time horizon. A regression analysis was conducted to explore the factors associated with vaccination delay. Results: Current DTaP vaccination was estimated to be delayed by 16, 27 and 44 days, for the first, second and third doses, respectively, relative to vaccination at exactly 60, 120 and 180 days. The model estimated that vaccination at exactly age 60, 120 and 180 days could prevent approximately 278 pertussis cases, 103 hospitalizations and 1 death in infants aged <1 year in the US, gaining approximately 38 quality-adjusted life years and saving approximately $1.03 million in healthcare costs. Conclusions: Timely administration of infant pertussis vaccine doses could potentially reduce subsequent pertussis cases, hospitalizations, deaths and medical costs in infants aged <1 year in the US.