https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(06)68848-X.pdf

Recent developments in pertussis

Pertussis is increasingly recognized as a source of infection in adults who then commonly infect young children. Immunity to illness caused by Bordetella pertussis is not long-lived, so optimal control of pertussis may require booster immunizations. In a cost-benefit analysis, we evaluated the benefits of 7 independent strategies for administering a pertussis booster, in the form of a diphtheria-tetanus-acellular pertussis vaccine, to adolescents and adults. Break-even vaccine costs for each strategy were calculated by dividing costs preventable by vaccine by the number of persons eligible for vaccination. Of these strategies, the most economical would be to immunize adolescents 10-19 years of age, which would prevent 0.7-1.8 million pertussis cases and save 0.6 dollars-1.6 billion dollars over a decade. Although justified by our analysis, routine adult booster vaccinations every decade would be more expensive and more difficult to implement. A recommendation for booster vaccinations every 10 years requires more information about duration of immunity, program costs, compliance, and nonmedical costs associated with pertussis.

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Evaluation of strategies for use of acellular pertussis vaccine in adolescents and adults: a cost-benefit analysis.

The potential cost-effectiveness of acellular pertussis booster vaccination in England and Wales.

The incidence of reported pertussis has increased during the past decade and poses a growing health and economic burden in developed countries, despite high rates of primary vaccination. Administration of a booster dose of acellular pertussis vaccine to adolescents may help reduce this burden, not only by reducing infections in vaccinated individuals but also by reducing transmission of Bordetella pertussis to other individuals, particularly infants. An epidemiologic model was created to assess the health and economic impact of implementing a program of routine acellular pertussis immunization in adolescents 11-18 years of age in the United States, considering both the reduction in cases in those vaccinated and among the unvaccinated population (due to herd immunity). Inputs for the base case were defined according to information derived from published literature and were supplemented by estimates provided by members of the Global Pertussis Initiative. Both direct and indirect costs were included (in 2002 US dollars) using U.S. data. Outcomes were evaluated over the lifetime of a cohort of potential adolescent vaccine candidates. Because of uncertainty in many of the inputs, extensive sensitivity analyses were conducted. With 80% vaccination coverage of adolescents and a 20% reduction of other cases because of herd immunity, >68,000 cases and 41 pertussis-related deaths would be avoided in the subsequent 10 years by routine administration of acellular pertussis boosters to a single cohort of adolescents in the United States. This strategy would be cost-effective, incurring from 6000 US dollars to 22,000 US dollars per life-year gained. The level of herd immunity attained and the true incidence of pertussis are critical determinants of cost effectiveness, as is the duration of immunity resulting from immunization. The cost of immunization and the discount rate also play a role. Although there is considerable uncertainty surrounding key inputs, the results indicate that the conditions required for adolescent immunization to be economically warranted are realistic.

Pertussis immunization of adolescents in the United States: an economic evaluation.

BACKGROUND: Despite widespread immunization programs, a clear increase in pertussis incidence is apparent in many developed countries during the last decades. Consequently, additional immunization strategies are considered to reduce the burden of disease. The aim of this study is to design an individual-based stochastic dynamic framework to model pertussis transmission in the population in order to predict the epidemiologic and economic consequences of the implementation of universal booster vaccination programs. Using this framework, we estimate the cost-effectiveness of universal adolescent pertussis booster vaccination at the age of 12 years in the Netherlands. METHODS/PRINCIPAL FINDINGS: We designed a discrete event simulation (DES) model to predict the epidemiological and economic consequences of implementing universal adolescent booster vaccination. We used national age-specific notification data over the period 1996-2000--corrected for underreporting--to calibrate the model assuming a steady state situation. Subsequently, booster vaccination was introduced. Input parameters of the model were derived from literature, national data sources (e.g. costing data, incidence and hospitalization data) and expert opinions. As there is no consensus on the duration of immunity acquired by natural infection, we considered two scenarios for this duration of protection (i.e. 8 and 15 years). In both scenarios, total pertussis incidence decreased as a result of adolescent vaccination. From a societal perspective, the cost-effectiveness was estimated at €4418/QALY (range: 3205-6364 € per QALY) and €6371/QALY (range: 4139-9549 € per QALY) for the 8- and 15-year protection scenarios, respectively. Sensitivity analyses revealed that the outcomes are most sensitive to the quality of life weights used for pertussis disease. CONCLUSIONS/SIGNIFICANCE: To our knowledge we designed the first individual-based dynamic framework to model pertussis transmission in the population. This study indicates that adolescent pertussis vaccination is likely to be a cost-effective intervention for The Netherlands. The model is suited to investigate further pertussis booster vaccination strategies.

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Cost-Effectiveness of Adolescent Pertussis Vaccination for The Netherlands: Using an Individual-Based Dynamic Model

Objective: Pertussis is a highly contagious infection affecting mainly children. Acellular pertussis vaccines were recently introduced in Canada based on evidence of improved safety and efficacy overwhole cell vaccines, the current standard of care. The following study reports the economic impact of replacing the whole cell vaccine (wP) by a new acellular vaccine (aP) in the Ontario pertussis immunisation programme. Design: For a hypothetical cohort of 100 000 children from birth to the age of 8 years, the costs and consequences of pertussis vaccination with either aP or wP were compared. A decision analytical modelwas constructed for vaccine delivery, treatment of pertussis cases and vaccine adverse events, with analyses from the viewpoints of the Ontario Ministry of Health and society. Main outcome measures and results: The main outcomes were expected number of pertussis cases, hospitalisations, and workdays lost by parents. Data on vaccine effectiveness, pertussis incidence, and other parameters used in the model were from published literature. Costs were discounted at 5%, and extensive sensitivity analyses were undertaken. Over 8 years, in a cohort of 100 000 children, the introduction of aP would prevent 10 500 cases of pertussis, avoiding 504 hospital admissions and 73 500 days of work absence. For Ontario, healthcare cost savings over the same period would amount to 275 585 Canadian dollars ($Can), and societal savings to $Can9 752 864 (1997values). Results were sensitive to both incidence of pertussis and vaccine efficacy. Conclusion: This study suggests that even though the new acellular vaccine has a higher acquisition cost than the currentwhole cell vaccine, its improved efficacy and safety result in overall cost savings.

Ron Gold

Papers

Economic Evaluation of a New Acellular Vaccine for Pertussis in Canada