Modelling strategic use of the national antiviral stockpile during the CONTAIN and SUSTAIN phases of an Australian pandemic influenza response

Abstract

Objective: To define optimum use of the national antiviral stockpile during the early phases of the response to pandemic influenza in Australia, to inform the 2008 revision of the Australian Health Management Plan for Pandemic Influenza.

Methods: A mathematical model was used to compare strategic uses of antiviral agents for treatment and post-exposure prophylaxis to limit transmission until availability of a strain-specific vaccine. The impact of provision of pre-exposure prophylaxis to healthcare workers (HCWs) on the ability to control the epidemic was also assessed.

Results: Optimal constraint of epidemic growth was achieved by intensive ascertainment of contacts of cases for post-exposure prophylaxis for as long as feasible. While pre-exposure prophylaxis of healthcare workers utilised a substantial proportion of the stockpile, this did not impede disease control or the ability to treat cases. Absolute delays to outbreak depended on both the intervention strategy and the growth rate of the epidemic. As vaccination was only effective when introduced before explosive growth, this timing was critical to success.

Conclusions and implications: Liberal distribution of antiviral drugs to limit disease spread for as long as is feasible represents optimal use of these agents to constrain epidemic growth. In reality, additional non-pharmaceutical control measures are likely to be required to control transmission until vaccines can definitively contain pandemic influenza outbreaks.