Adult pertussis vaccination strategies and their impact on pertussis in the United States: evaluation of routine and targeted (cocoon) strategies

Abstract

A compartmental, age-structured mathematical model was developed and recent US pertussis epidemiology data were used to evaluate the impact on pertussis infection rates of routine and targeted adult immunization strategies. Model simulations predict that the implementation of adolescent immunization only could reverse the current rise in pertussis infection rates but may lead to a resurgence of pertussis in subsequent decades. In contrast, inclusion of a routine adult strategy is likely to lead to sustained control of pertussis. Routine adult vaccination could control the disease even with relatively low coverage rates of 40% for routine vaccination of all adults every 10 years, or 65% for a targeted vaccination of close contacts of newborns completed by one booster dose for all adults. The model also predicts that the optimal age for this booster dose is 40 years. These results support the 2006 American Academy of Immunization Practices' recommendations for adolescent and adult vaccination against pertussis.

Fig. 1

Diagram of the immunological and infectious states and transitions between states in the age-specific pertussis model. WN1–3, Waning of natural immunity 1–3; V1–V4, vaccination status 1–4; WV1–3, waning vaccine 1–3; vc, vaccine coverage.

Fig. 2

(a) Annual, age-specific incidence of pertussis (■, typical cases; □, mild cases) derived from the model for the current vaccination schedule (base case). (b) Comparison of the age-specific force of infection in absence of vaccination used in Van Rie & Hethcote [8] and derived from US data in this analysis.

Fig. 3

Evolution over time of the annual incidence of symptomatic pertussis. vc, Vaccination coverage.

Fig. 4

Annual, age-specific incidence of symptomatic (typical+mild) pertussis cases once steady state situation has been reached. vc, Vaccination coverage.

Fig. 5

Impact of the age of adult booster dose of pertussis vaccine on the annual pertussis incidence and on the annual number of vaccinations needed.

Fig. 6

Impact of vaccination coverage rate on annual pertussis incidence and annual number of vaccinations by adult vaccination strategy. (a) Childhood+adolescent+cocoon strategy. (b) Childhood+adolescent+routine adult every 10 years.