Medical Studies

Influenza Vaccination: Part II

How does one measure the cost effectiveness of flu vaccination? Today we will examine a paper which attempts to do just that.

Nichol, et al. (2003) preforms a cost-benefit analysis of live attenuated influenza vaccination (LAIV) for healthy, working adults. This type of vaccination is administered through a nasal spray than through an intramuscular shot. The authors attempted to answer this question using a multi-center, randomized, double blind placebo controlled trial. They found that adult influenza vaccinations decreased the number of work days missed by 18%, decreased the number of less effective work days by 18% and decreased the number of provider visits by 13%. This amounts to a large benefit to society, but one must also estimate the costs of vaccination in order to have an accurate cost-benefit analysis. Nichol and colleagues estimate the costs as follows:


Costs of vaccination
Direct costs of vaccination Costs of vaccine and administration
Indirect costs of vaccination P(missing work for Vac.) x (hrs of work missed for Vac.) x (wage)
Direct costs of side effects due to vaccination P(side effects)x (provider visit cost)
Indirect costs of side effects due to vaccination P(side effect lead to work loss)x(wage)x(8 h/day)

Costs averted due to vaccination
Direct costs of medical care averted due to vaccination P(provider visit from illness among NV) x (1 − RR_V) x (cost of provider visit)
Indirect costs of work loss averted due to vaccination P(work loss due to illness among NV)x(1 − RR_V)x(wage)x(8h/day)
Indirect costs of reduced work effectiveness P(reduced work effectiveness_NV) x (1- RR_V) x (wage) x (8h/day)

Provider visit costs is estimated separately for influenza-like illness (ILI) and upper respiratory tract illness. Costs include not only physician time, but also the average number of tests and procedures ordered and medications prescribed (e.g.: antibiotics, Rx and over the counter meds) and are estimated using NAMCS data. The authors find that the break even cost of flu vaccinations for healthy adults is $43.07. Monte Carlo simulation is then used to prove their results more robust.

The study does have some problems. The authors do not include overhead costs in their estimate of physician visits. Secondly, no justification is found for the distributional assumptions of the Monte Carlo simulations. Most distributions are triangular between the min and the max.