Prevention with shot. Prevention is the best answer. Although the flu vaccine isn't 100%, it offers your best chance of avoiding or getting a milder case of influenza. If you have influenza and you've been sick <48hr, your doctor might prescribe tamiflu (oseltamivir). Influenza ususally lasts 7-10days, and tamiflu (oseltamivir) only reduces the duration by 1-2 days, so even with tamiflu (oseltamivir), you won't feel better quickly, but may be less severe.