Zanamivir Versus Trivalent Split Virus Influenza Vaccine

Several studies have demonstrated that zanamivir and oseltamivir are effective in preventing influenza infection and illness when used either as prophylaxis after exposure to a household contact with influenza or when taken for several weeks at the height of influenza activity in the general community. However, the longest duration of prophylaxis with neuraminidase inhibitors in two clinical trials, to date, has been six weeks.

Antiviral medication will likely have an important role in the response to the next influenza pandemic. Additionally, there may be indications for use during seasons when the major infecting strain of influenza in not one whose antigen is well covered by the vaccine.

Inclusion criteria

• 18-69 years old as of 01/Nov/2008
• have an understanding of the study, agree to its provisions, and give written informed consent prior to study entry
• available for follow-up during the study period
• if a women of child-bearing years, must meet criteria to prevent pregnancy

Exclusion criteria

• allergy to any component of influenza vaccine or zanamivir
• previous serious adverse event associated with influenza vaccination
• receipt of influenza vaccine between 01/Mar/2008 and start of study
• previous adverse event associated with the use of antiviral medications
• expecting to be unable to take zanamivir for more than 72 hours during study period
• planning to spend more than 2 consecutive weeks outside Canada or more than 100 km from the study site during study period
• pregnant, or planning to become pregnant, during study period
• breastfeeding, or planning to breastfeed, a child under 12 months of age during study period
• receipt of immunoglobulin within six months of study entry
• immunocompromising condition or therapy that would be expected to reduce the efficacy of vaccination
• plans to receive cytotoxic or radiation therapy during study period
• history of cardiovascular or pulmonary disease that has required hospital admission within the past year
• history of asthma or other chronic respiratory disease
• participating in a trial that will result in the receipt of an investigational medication during the period that zanamivir may be taken (15/Nov/2008 to 30/Apr/2009)