Purpose: Some authorities recommend varicella antibody testing or vaccination for adults without a history of chickenpox, but the cost effectiveness of these interventions is uncertain.
Subjects and methods: Using a Markov decision model, we estimated the cost effectiveness of three strategies for adults with no history of chickenpox: no vaccination, varicella antibody testing followed by vaccination for those without antibody, and vaccinating all. Societal and third-party payer perspectives were taken, with costs and benefits discounted at 3% per year. Assumptions for the baseline analysis were chosen to bias against no vaccination.
Results: In the baseline analysis for 20- to 29-year-old patients, testing followed by vaccination compared with no vaccination is cost saving from a societal perspective and costs $6,670 per quality-adjusted life-year (QALY) gained from a third-party payer perspective. When less favorable assumptions are used, results are sensitive to the rates of compliance with vaccination follow-up; testing followed by vaccination costs more than $50,000 per QALY if <75% comply. For patients 30 years of age and older, the incremental cost of testing followed by vaccination is at least $97,100 per QALY compared with no vaccination, with costs greater than $50,000 per QALY unless testing costs less than $7.73, the chickenpox case-fatality rate is >0.067% (baseline 0.025%), or immunity with no chickenpox history is <25% (baseline 71%). In either age group, vaccinating all has an incremental cost of $2 to $16 million per QALY gained compared with testing followed by vaccination.
Conclusion: Testing followed by vaccination for varicella in US adults aged 20 to 29 years may be cost effective by conventional criteria but is sensitive to rates of compliance with vaccination protocols. Testing or vaccination of older adults is expensive but may be cost effective in patients with lower probabilities of immunity or in those who have a greater risk of complications from chickenpox.