EVALUATING STOCKPILING AND UTILIZATION STRATEGIES FOR INFLUENZA PROPHYLAXIS: A DYNAMIC MODELING APPROACH

Purpose: Antivirals have been shown to be effective in the prevention and treatment of influenza infection.  Oseltamivir (and, to a lesser extent, zanamivir) have been stockpiled by some institutions to protect their employees and maintain business continuity during a potential influenza pandemic.  The goal of this study was to evaluate the impact of various prophylaxis stockpiling and utilization strategies on employee absenteeism.

Methods: We created a deterministic compartmental model with two distinct populations: the general public population and a particular institution considering stockpiling antivirals.  The epidemic process is described by a system of nonlinear differential equations, with baseline disease transmission parameters estimated from the literature on seasonal and pandemic influenza.

Results: A pandemic with a basic reproductive number of 2.5 resulted in peak absenteeism of 15.7%.  The table shows variation in absenteeism and total cases based on different coverage, duration, and timing of prophylaxis scenarios.  Early initiation and longer duration were associated with the lowest absenteeism; in contrast, longer duration and greater coverage were associated with the lowest total cases.  The worst outcomes occurred with early initiation of short-course prophylaxis for the entire workforce, leading to a second epidemic wave (graph not shown).

(Early starting time is the day when 1% of the employees are symptomatic; late starting time is the day when 5% of the employees are symptomatic. We assume a 2-day campaign with 92% prophylaxis effectiveness for an institution with 5000 employees)

Conclusion: Workforce protection against pandemic influenza is theoretically possible with early initiation of long-course prophylaxis in the majority of workers.  Short-course prophylaxis may be associated with worse outcomes due to a second wave phenomenon.