This patient should be given postexposure prophylaxis with the inactivated influenza vaccine and oseltamivir chemoprophylaxis. Outbreaks of seasonal influenza virus infection generally occur during autumn and winter but may last into the spring. Most severe outbreaks are related to influenza A viruses, but they may also occur with type B influenza virus. Yearly preexposure immunization is recommended for all persons age 6 months or older, assuming no contraindications. In patients who have not been immunized, chemoprophylaxis with the neuraminidase inhibitors oseltamivir or zanamivir is recommended for persons who have been exposed to someone known or suspected of having active influenza, but only if the antivirals can be started within 48 hours of the most recent exposure. Both medications have activity against influenza A and B viruses, with resistance occurring in less than 1% of strains. However, zanamivir, which is administered by oral inhalation, is contraindicated in persons with chronic respiratory conditions, including those with asthma, such as this patient. Because chemoprophylaxis lowers but does not eliminate the risk for influenza, immunization with an influenza vaccine preparation should also be provided. Despite this patient's concern, the relative and attributable risks of neurologic sequelae such as Guillain-Barré syndrome after seasonal influenza vaccination are lower than those that occur in association with influenza infection.

The adamantine medication amantadine does not have activity against influenza B, and increasing drug resistance among influenza A strains make it an inappropriate medication for chemoprophylaxis.

The live-attenuated influenza vaccine given by nasal mist is approved only for persons age 2 to 49 years and would therefore not be appropriate in this patient.