One should be considered for post-exposure anti-influenza chemoprophylaxis when: The illness seen shortly after the influenza vaccination. People who vaccine is contraindicated (including anaphylaxis to egg) History of Guillain-Barre Syndrome within weeks of previously admnistered vaccine Unvaccinated in close contact with those high risk of developing influenza complications All residents of long term facilities ot nursing home, including those already vaccinated. Immunocompromised people People who were unable to get vaccine due to shortage, if the person is at high risk of developing complication of influenza. The suggested chemoprophylactic regime is: Oselatmivir PO: a. 3 months to < 1 y/o: 3 mg/kg OD b. > 1 y/o and BW < 15kg: 30mg OD c. 15 - 23 kg: 45mg OD d. 23 - 40 kg: 60mg OD e. > 40kg and adults: 75mg OD Reference: BMJ Best Practice