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Volume 17, Number 9—September 2011


Estimating Effect of Antiviral Drug Use during Pandemic (H1N1) 2009 Outbreak, United States

Charisma Y. Atkins, Anita Patel, Thomas H. Taylor, Matthew Biggerstaff, Toby L. Merlin, Stephanie M. Dulin, Benjamin A. Erickson, Rebekah H. Borse, Robert Hunkler, and Martin I. Meltzer
Author affiliations: Author affiliations: Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (C.Y. Atkins, A. Patel, T.H. Taylor, Jr., M. Biggerstaff, T.L. Merlin, S.M. Dulin, B.A. Erikson, R.H. Borse, M.I. Meltzer); IMS Health, Fountain Hills, Arizona, USA (R. Hunkler)

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Table 2

Input values used to estimate influenza antiviral drug–related reduction in hospitalizations during pandemic (H1N1) 2009 outbreak in the United States, April 24, 2009–March 26, 2010

Input Initial value Sources
Distribution of prescriptions by patient age group, y* IMS Health Xponent database (3)
0–17 38.6%
18–64 53.4%
Prescriptions filled for prophylaxis† 10% Assumption: Some prescriptions were written to prevent infection and disease without presentation of symptoms.
Prescriptions for patients who failed to adhere to drug regimen or used for personal stockpiles
Assumption: Not all patients will adhere with the drug regimen as prescribed. Also, some prescriptions were for personal stockpiles
Antiviral drug effectiveness against hospitalization, by age group, y‡ Literature review (see Table 3)
0–17 22%–32%
18–64 34%–50%
Median (range) risk for hospitalization, given pandemic (H1N1) 2009–related illness, by age group, y§ Reed et al. (4)
0–17 0.0038 (0.00314–0.00428)
18–64 0.00496 (0.0041–0.00558)
>65 0.0155 (0.0128–0.0174)

*Age group–based distribution of prescriptions based on IMS (IMS Health, Norwalk, CT, USA) that covered prescriptions written for oseltamivir (only) from October 9, 2009, through March 26, 2010.
†These inputs were subjected to sensitivity analyses (see Table 4).
‡Effectiveness estimate assumes that the patient follows the drug regimen, i.e., these estimates do not allow for those who do not take the complete course. Failure to follow prescribed drug regimen was assumed to have 0% effect on reducing risk of hospitalization. This assumption was accounted for in a separate input.
§Risk of per-person hospitalization, given symptomatic illness caused by pandemic (H1N1) 2009 virus.

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