Abstract
ObjectivesHealth benefits and costs of combined reduced-antigen-content tetanus, diphtheria, and pertussis (Tdap) immunization among adults ≥65 years have not been evaluated. In February 2012, the Advisory Committee on Immunization Practices (ACIP) recommended expanding Tdap vaccination (one single dose) to include adults ≥65 years not previously vaccinated with Tdap. Our study estimated the health and economic outcomes of one-time replacement of the decennial tetanus and diphtheria (Td) booster with Tdap in the 10% of individuals aged 65 years assumed eligible each year compared with a baseline scenario of continued Td vaccination.MethodsWe constructed a model evaluating the cost-effectiveness of vaccinating a cohort of adults aged 65 with Tdap, by calculating pertussis cases averted due to direct vaccine effects only. Results are presented from societal and payer perspectives for a range of pertussis incidences (25–200 cases per 100,000), due to the uncertainty in estimating true annual incidence. Cases averted were accrued throughout the patient 's lifetime, and a probability tree used to estimate the clinical outcomes and costs (US$ 2010) for each case. Quality-adjusted life-years (QALYs) lost to acute disease were calculated by multiplying cases of mild/moderate/severe pertussis by the associated health-state disutility; QALY losses due to death and long-term sequelae were also considered. Incremental costs and QALYs were summed over the cohort to derive incremental cost-effectiveness ratios. Scenario analyses evaluated the effect of alternative plausible parameter estimates on results.ResultsAt incidence levels of 25, 100, 200 cases/100,000, vaccinating adults aged 65 years costs an additional $336,000, $63,000 and $17,000/QALY gained, respectively. Vaccination has a cost-effectiveness ratio less than $50,000/QALY if pertussis incidence is >116 cases/100,000 from societal and payer perspectives. Results were robust to scenario analyses.ConclusionsTdap immunization of adults aged 65 years according to current ACIP recommendations is a cost-effective health-care intervention at plausible incidence assumptions.
Highlights
The incidence of pertussis substantially declined immediately following the introduction of reduced-antigen-content tetanus, diphtheria and acellular pertussis (Tdap) vaccination recommendations in 1997 and 2005, thereafter rates have steadily increased to the point that pertussis causes a significant burden of disease in the US [1,2]
In 2005, the Advisory Committee on Immunization Practices (ACIP) recommended that adolescents 11–18 years of age and adults aged 19–64 years should receive a single dose of Tdap vaccine, instead of the standard tetanus and reduced-antigen-content diphtheria (Td) decennial booster [1]
Recommended expanded use of Tdap, advising that children aged 7 through 10 years not previously fully vaccinated against pertussis receive a single dose of Tdap, and that adults $65 years who have close contact with an infant receive a single dose of Tdap if they have not previously received the booster [3]
Summary
In 2005, the Advisory Committee on Immunization Practices (ACIP) recommended that adolescents 11–18 years of age (preferably at age 11–12 years) and adults aged 19–64 years should receive a single dose of Tdap vaccine, instead of the standard tetanus and reduced-antigen-content diphtheria (Td) decennial booster [1]. Serologic studies have suggested that the true incidence in adults may be more than 100 times the incidence reported to the Centers for Disease Control and Prevention (CDC) [6,7]. Despite this uncertainty, current evidence clearly suggests that recent vaccination practices have not completely controlled the risk of pertussis infection
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