Anti-viral chemotherapy plays an important part in treating and preventing influenza illness. However, its effectiveness in severe infections can be debated and a reoccurring problem is the emergence of resistant virus. Passive immunisation has for a long time been and is still used for prophylaxis and treatment of a number of infectious diseases. In this experimental study anti-influenza antibodies were passively administrated to mice, subsequently they were infected with influenza virus and

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... eated with oseltamivir. The aim was to investigate, if anti-influenza antibodies influenced the out come of oseltamivir treatment and development of resistance towards oseltamivir. We show, that oseltamivir alone was not able to effectively prevent a fatal outcome, but that oseltamivir administered together with a limited amount of antibodies, resulted in improvement of the clinical condition of the mice. The results also showed that a higher dosage of antibodies alone were able to protect the mice from a lethal dose of virus. These findings suggest that the effectiveness of oseltamivir depends on the host's immune response to the influenza virus, and that that passive immunization is an option that should be considered in the in control of influenza.