Influenza Exposure Treatment Guidelines

Introduction to Postexposure Chemoprophylaxis

The American College of Physicians and Infectious Diseases Society of America recommend postexposure antiviral chemoprophylaxis for asymptomatic individuals at very high risk of complications, such as severely immunocompromised patients, and unvaccinated household contacts of very high-risk individuals, initiated within 48 hours of exposure 1, 2
Postexposure chemoprophylaxis should be reserved primarily for individuals at very high risk of complications, and should not be routinely given to all exposed individuals 1, 2

Asymptomatic adults and children ≥3 months who are at very high risk of developing complications, such as severely immunocompromised persons, are eligible for postexposure chemoprophylaxis after household exposure to influenza 1, 2, 3
Unvaccinated adults and children ≥3 months who are household contacts of persons at very high risk of complications from influenza are also eligible for postexposure chemoprophylaxis after exposure to influenza 1, 2, 3

Postexposure chemoprophylaxis must be initiated as soon as possible after exposure, ideally no later than 48 hours after exposure 1, 2, 3
Do not administer once-daily postexposure chemoprophylaxis if >48 hours has elapsed since exposure; instead, educate the patient to initiate full-dose empiric antiviral treatment as soon as symptoms occur 1, 2, 3

Use a neuraminidase inhibitor, such as inhaled zanamivir or oral oseltamivir, rather than an adamantane antiviral, due to high resistance rates 1, 2, 3
Baloxavir is also FDA-approved for postexposure prophylaxis as a single dose within 48 hours of exposure for patients ≥12 years 5

Administer postexposure chemoprophylaxis for 7 days after the most recent exposure to a close contact with influenza in a nonoutbreak setting 1, 2, 3

An alternative to postexposure chemoprophylaxis is educating patients and arranging for early empiric initiation of antiviral treatment if symptoms develop, which may be preferable in many situations to avoid unnecessary medication exposure 1, 2, 3

If a person receiving postexposure chemoprophylaxis becomes symptomatic, immediately test for influenza and switch to full antiviral treatment dosing, preferably with an antiviral drug with a different resistance profile if not contraindicated 1, 2, 3

Do not use chemoprophylaxis as a substitute for vaccination; the influenza vaccine should always be offered when not contraindicated 5
Do not routinely give prophylaxis to all exposed individuals; reserve for specific high-risk groups outlined above 1, 2
Do not delay treatment if symptoms develop while on prophylaxis; switch immediately to treatment dosing 1, 2

In long-term care facilities or hospitals, outbreak control measures, including antiviral chemoprophylaxis of residents/patients, should be implemented when 2 cases of healthcare-associated laboratory-confirmed influenza are identified within 72 hours of each other in residents or patients of the same ward or unit 1, 2