• postexposure prophylaxis;
  • oseltamivir;
  • influenza;
  • long-term care;
  • cost-effectiveness

Objectives: To compare the cost-effectiveness of oseltamivir postexposure prophylaxis during influenza A outbreaks with that of amantadine postexposure prophylaxis or no postexposure prophylaxis in long-term care facilities (LTCFs).

Design: Cost-effectiveness analysis based on decision analytic model from a government-payer perspective.

Setting: A Canadian LTCF, with high staff vaccination, at the beginning of influenza season.

Participants: Elderly, influenza-vaccinated patients living in a Canadian LTCF.

Measurements: Incremental costs (or savings) per influenza-like illness case avoided compared with usual care.

Results: From a government-payer perspective, this analysis showed that oseltamivir was a dominant strategy because it was associated with the fewest influenza-like illness cases, with cost savings of $1,249 per 100 patients in 2001 Canadian dollars compared with amantadine and $3,357 per 100 patients compared with no prophylaxis. Costs for amantadine dose calculation and hospitalization for adverse events contributed to amantadine being a more-expensive prophylaxis strategy than oseltamivir. Both prophylaxis strategies were more cost-effective than no prophylaxis.

Conclusion: Despite high influenza vaccination rates, influenza outbreaks continue to emerge in LTCFs, necessitating cost-effective measures to further limit the spread of influenza and related complications. Although amantadine has a lower acquisition cost than oseltamivir, it is associated with more adverse events, lower efficacy, and individualized dosing requirements, leading to higher overall costs and more influenza-like illness cases than oseltamivir. Therefore the use of oseltamivir postexposure prophylaxis is more cost-effective than the current standard of care with amantadine prophylaxis or no prophylaxis.