G01

Assessing Adolescent Immunization Options for Pertussis in Canada: a Cost-Utility Analysis
Kikanwa Anyiwe1,2, Marina Richardson1,2, Jason Brophy3,4, Oliver Baclic5, Beate Sander1,2,6,7
1Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, ON, Canada. 2Toronto Health Economics and Technology Assessment (THETA) Collaborative, University Health Network, Toronto, ON, Canada. 3Department of Pediatrics, University of Ottawa, Ottawa, ON, Canada. 4Division of Infectious Diseases, Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada. 5Centre for Immunization and Respiratory Infectious Diseases, Public Health Agency of Canada, Ottawa, ON, Canada. 6Institute for Clinical Evaluative Sciences, Toronto, ON, Canada. 7Public Health Ontario, Toronto, ON, Canada

Abstract

Objective: In Canada, adolescent pertussis vaccination helps prevent transmission. Trade-offs with respect to disease prevention and effectiveness can be associated with immunization timing. The objective of this study is to assess the cost-utility of different adolescent pertussis immunization strategies. Methods: A cost-utility analysis was conducted using a Markov model, with adolescents (beginning at age 10 years) as the cohort of interest. The model assessed three vaccination strategies: 1) immunization of 10 year olds, 2) removal of adolescent vaccination, or 3) immunization of 14 year olds (status quo comparator). The analysis was conducted from a healthcare payer perspective and used a lifetime time horizon. Primary outcomes included life years, quality-adjusted life years (QALYs), health system costs, and incremental cost-effectiveness ratio (ICER). Costs and outcomes were discounted at 1.5% annually. Deterministic and probabilistic sensitivity analysis was conducted to assess parameter uncertainty. Results: The current recommended adolescent immunization strategy (at 14 years old) resulted in an average of 40.4432 expected QALYs at a cost of $34.36 per individual. This strategy was dominated by immunization at 10 years and no immunization. Compared to no immunization, immunizing at 10 years of age had an ICER of $108,703.01 per QALY. Results were robust across a series of deterministic and probabilistic sensitivity analyses; findings were most sensitive to infection probability, vaccine cost, vaccine effectiveness, probability of mortality, and cost of inpatient care. At a cost-effectiveness threshold of $50,000/QALY, removal of the adolescent vaccine represented the most cost-effective strategy in 97% of simulations. However, at a threshold of $100,000/QALY, immunization at 10 years of age is marginally cost-effective relative to no immunization, with a 58% probability of being cost-effective. Conclusion: Findings suggest that alternatives to the current Canadian adolescent pertussis vaccine schedule – especially no immunization – are more cost-effective relative to current immunization of 14 year olds.