Inpharma 1621 - 19 Jan 2008

Dynamic modelling captures herdeffect in influenza vax

Analysing the epidemiological behaviour of infectiousdiseases requires the use of dynamic models that allowfor the inclusion of the herd immunity effect, sayresearchers from Spain. If such immunity is not takeninto account, the effectiveness of the prophylacticmeasures employed would be severelyunderestimated, they contend.

The researchers modelled the progress of an influenzavirus epidemic in Spain, using a decision-tree analysis;they compared the results of a dynamic model withthose obtained using a static model, to assess theeffectiveness of an influenza vaccination programme tothe Spanish NHS.

Over a 1-year time horizon, the static model showedthat influenza vaccination would likely be inefficient,with a return rate of 0.28 per € invested by the NHS.*However, when the dynamic modelling approach wasemployed, the return on investment rate increased to1.22 per €. In the dynamic model, the cost associatedwith vaccination would need to be ≥ €17.19 per personfor vaccination to inefficient, versus €4 if the staticapproach was applied.

The dynamic modelling approach allows analysis ofthe intervention in terms of both the direct effects on theefficaciously vaccinated individuals and the indirecteffects on the remaining target population, which takesadvantage of the herd immunity effect, the researcherscomment.* Costs were calculated in 2005 values from the perspective of thehealthcare payer, and included those associated with vaccinationacquisition and administration, and emergency- and primary-careconsultations.

Pradas-Velasco R, et al. Dynamic modelling of infectious diseases: an applicationto the economic evaluation of influenza vaccination. PharmacoEconomics 26:45-56, No. 1, 2008 801055662

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Inpharma 19 Jan 2008 No. 16211173-8324/10/1621-0001/$14.95 Adis © 2010 Springer International Publishing AG. All rights reserved