What treatment is recommended for influenza exposure?

Treatment for Influenza Exposure

Postexposure antiviral chemoprophylaxis is selectively recommended—not routinely given to all exposed individuals—and should be reserved primarily for asymptomatic persons at very high risk of complications (such as severely immunocompromised patients) or unvaccinated household contacts of very high-risk individuals, initiated within 48 hours of exposure. 1

Who Should Receive Postexposure Chemoprophylaxis

Very High-Risk Patients (Strongest Indication)

• Asymptomatic adults and children ≥3 months who are at very high risk of developing complications (e.g., severely immunocompromised persons such as hematopoietic stem cell transplant recipients) and for whom influenza vaccination is contraindicated, unavailable, or expected to have low effectiveness, after household exposure to influenza 1

Unvaccinated Household Contacts of High-Risk Persons

• Unvaccinated adults and children ≥3 months who are household contacts of persons at very high risk of complications from influenza (e.g., severely immunocompromised persons), after exposure to influenza—this should be given in conjunction with influenza vaccination 1

Optional Consideration for Other Groups

• Unvaccinated adults and children ≥3 months who are at high risk of developing complications (but not "very high risk") when influenza vaccination is expected to be effective but not yet administered—short-term chemoprophylaxis can be considered in conjunction with prompt vaccination 1
• Unvaccinated adults (including healthcare personnel) and children ≥3 months who are in close contact with high-risk persons during periods of influenza activity when vaccination is contraindicated or unavailable and these high-risk persons are unable to take chemoprophylaxis 1

Critical Timing Requirements

Postexposure chemoprophylaxis must be initiated as soon as possible after exposure, ideally no later than 48 hours after exposure. 1

• 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, if treatment is indicated 1

Recommended Medications and Dosing

Use a neuraminidase inhibitor (NAI)—specifically inhaled zanamivir or oral oseltamivir—rather than an adamantane antiviral (amantadine/rimantadine are not recommended due to high resistance rates). 1

Oseltamivir Dosing for Prophylaxis

• Adults and adolescents ≥13 years: 75 mg orally once daily 2
• Pediatric patients 1-12 years: weight-based once-daily dosing (15 kg or less: 30 mg once daily; 15.1-23 kg: 45 mg once daily; 23.1-40 kg: 60 mg once daily; >40 kg: 75 mg once daily) 2
• Baloxavir is also FDA-approved for postexposure prophylaxis as a single dose within 48 hours of exposure for patients ≥12 years 1

Duration of Prophylaxis

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

• For seasonal prophylaxis during community outbreaks: continue for at least 10 days following close contact with an infected individual and up to 6 weeks during a community outbreak 2
• In immunocompromised patients, prophylaxis may be continued for up to 12 weeks 2

Important Alternative Strategy

An alternative to postexposure chemoprophylaxis is educating patients and arranging for early empiric initiation of antiviral treatment if symptoms develop—this approach may be preferable in many situations to avoid unnecessary medication exposure. 1

• This strategy involves providing the patient with a prescription for full-dose treatment (oseltamivir 75 mg twice daily for 5 days) to be initiated immediately upon symptom onset 3

Critical Monitoring and Switching to Treatment

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

• Treatment dose for oseltamivir: 75 mg twice daily (not once daily) for 5 days 3, 2

Common Pitfalls to Avoid

• Do not use chemoprophylaxis as a substitute for vaccination—the influenza vaccine should always be offered when not contraindicated 1
• Do not routinely give prophylaxis to all exposed individuals—this is not cost-effective and may promote resistance; reserve for the specific high-risk groups outlined above 1
• Do not delay treatment if symptoms develop while on prophylaxis—switch immediately to treatment dosing 1
• Nausea and vomiting occur in approximately 10-15% of patients taking oseltamivir; taking it with food reduces gastrointestinal side effects 3

Special Institutional Settings

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

• In institutional outbreaks, chemoprophylaxis should be administered for 14 days and continue for at least 7 days after the onset of symptoms in the last case identified 1