This aim of this project is to evaluate the efficacy of neuraminidase inhibitors as short-term prophylaxis against pandemic influenza infection in people who have close familial contact with the disease. The study is observational only. The primary measure used in this study will be the incidence of symptomatic pandemic influenza in patients receiving prophylaxis. Seroconversion to pandemic influenza, the incidence of adverse events and the relative effectiveness of oseltamivir and zanamivir prophylaxis will also be examined. This project will commence upon pandemic influenza being declared in Australia, Hong Kong or Singapore. Data will be analysed as quickly as possible to help inform the continued use of neuraminidase inhibitor therapy as a cornerstone of the public health agency response to pandemic influenza.

The aim of this study is to

1. Describe the effectiveness of short-term prophylaxis against symptomatic pandemic influenza infection
2. Describe the safety of short-term prophylaxis
3. Describe the seroconversion rate against pandemic influenza among recipients of short-term prophylaxis

The study is an open label prospective cohort study. Contact group members of people with diagnosed influenza who are recommended to receive NA inhibitor prophylaxis for short periods of time will be enrolled following provision of informed consent. Each episode of short-term prophylaxis will be recorded separately.

By design it is hoped that volunteers in this study who develop symptoms and signs of pandemic influenza infection will be enrolled in the Index Case (PIPET A) protocol with follow-up as required.

Inclusion Criteria:

• Provision of written informed consent
• Intention to commence or have commenced short-term prophylaxis with a neuraminidase inhibitor in individuals who have been exposed to the pandemic virus

Exclusion Criteria:

• none

Contact group members of people with diagnosed influenza who are recommended to receive NA inhibitor prophylaxis for short periods of time will be enrolled following provision of informed consent. Each episode of short-term prophylaxis will be recorded separately.