Antiviral drugs for influenza are an important adjunct to influenza vaccine for the treatment and prevention of influenza. However, they are not a substitute for vaccination.
Treatment with neuraminidase inhibitors (NI) such as oseltamivir and zanamivir is extremely variable between countries and is usually restricted to the very ill. Treatment with NI should only be considered where there is a reasonable likelihood that the patient has been exposed to the influenza virus. Additionally, treatment needs to begin as early as possible after the onset of illness, i.e. within 48 hours. In the at-risk groups, NI treatment may reduce serious illness and complications. After all, in some instances, vaccine effectiveness might be lower than in younger healthy adults, particularly if the patient is immunocompromised. Therefore, antiviral therapy could be considered even in vaccinated high-risk individuals with proven or strongly suspected influenza.
Influenza vaccination is still the primary method of influenza prevention, however NI prophylaxis can be a useful addition in some circumstances. Prophylaxis for seasonal influenza may be an option for the following individuals:
- Those at high risk of severe disease and morbidity who have not been vaccinated before the start of the influenza season;
- Those who have contraindications to vaccination;
- Those who refuse vaccination.
Whilst prophylaxis is effective, it may require 8-12 weeks of treatment. The other use of prophylaxis is in the prevention or control of influenza outbreaks, particularly among high-risk populations in institutional settings whether they have been vaccinated or not.