Influenza A (H1N1) virus is the most relevant virus in death by flu complications. Oseltamivir and zanamivir are used for influenza prophylaxis in epidemics. We aimed to evaluate the efficacy of chemoprophylaxis for influenza A (H1N1) for the Brazilian health care system.

We systematically searched the literature to identify efficacy results. Costs assessed from the system perspective were obtained from official Brazilian Ministry of Health systems, and completed from medical care at a university hospital of Campinas, Sao Paulo. Model outcomes were quality-adjusted life years (QALY) with willingness to pay BRL 30,000 (USD 8,212)/QALY and prevention of H1N1. A decision-tree model was used to calculate the incremental cost-effectiveness ratios for prophylaxis, compared to no prophylaxis. Deterministic and probabilistic sensitivity analyses were used to test robustness of the model.

Prophylaxis had 70 percent adherence to treatment, 9 percent adverse events, effectiveness in avoiding H1N1 (relative risk = 0.43; 95% confidence interval: 0.33, 0.57); no evidence of prophylaxis efficacy for complication, hospitalization and death was found. Both scenarios had 14 percent H1N1 attack rate, 67 percent of ambulatorial consult, 43 percent of inpatient care, 14 percent of deaths in hospital, 23 percent of intensive care where death was 40 percent. Utility was 0.50 during H1N1 infection, 0.23 with hospitalization, 0.195 less with adverse events, 0 for deaths and 0.885 for healthy. Cost was BRL39 (USD 11) for chemoprophylaxis; BRL 12 (USD 4) for outpatient care; BRL 5,728 (USD 1,568) for hospital admission; BRL 19,217 (USD 5,260) for intensive care; and BRL 292 (USD 80) for adverse events. Incremental cost of prophylaxis was BRL 40 (USD 11) and utility increased 0.004, which mean saving of BRL 2,921 (USD 780)/QALY. Prophylaxis saves BRL 338 (USD 92) per H1N1 case avoided. Univariate and probabilistic sensitivity analysis assure the robustness of results, with 43 percent probability of being of lower cost and higher effectiveness.

Prophylaxis is cost-effective from the health care system perspective using utility and avoided H1N1 cases outcomes.