Oseltamivir Prophylaxis for Influenza in Household or Close Contact Settings
For household contacts or close contacts of influenza-infected individuals, oseltamivir (Tamiflu) 75 mg once daily for 10 days is the recommended prophylactic regimen, which should be started as soon as possible after exposure and within 48 hours of symptom onset in the infected person. 1, 2
Prophylactic Regimen Based on Age and Weight
- For adults and adolescents (≥13 years): 75 mg once daily for 10 days 1
- For children 1-12 years (weight-based dosing):
- For children 3 months to <12 months: 3 mg/kg once daily for 10 days 2
- Not recommended for children <3 months unless situation is judged critical 2
Effectiveness of Prophylaxis
- Oseltamivir has demonstrated 82-89% protective efficacy in preventing laboratory-confirmed influenza illness in household contacts 2, 3
- Prophylaxis effectively prevents outbreaks within households with 84% protective efficacy for households 3
- One study found a 93-94% protective efficacy with a shorter 3-day regimen, though the standard recommendation remains 10 days 4
When to Start Prophylaxis
Prophylaxis should be initiated in the following circumstances:
- For household or close family contacts of a confirmed influenza patient, due to potential exposure to both the index case and common environmental sources 2
- Within 48 hours of symptom onset in the infected person 1, 3
- For high-risk individuals who have not yet been vaccinated or are within 2 weeks of vaccination 2
- For unimmunized family members or healthcare personnel with close exposure to high-risk unimmunized children or infants <24 months 2
- For control of influenza outbreaks in institutional settings with high-risk individuals 2
Duration of Prophylaxis
- Standard post-exposure prophylaxis: 10 days after last known exposure 2
- For community outbreaks: up to 6 weeks during periods of influenza activity 2
- For immunocompromised patients: may be extended up to 12 weeks 1
Important Considerations and Caveats
- Chemoprophylaxis is not a substitute for vaccination, which remains the primary means of influenza prevention 2
- Oseltamivir prophylaxis does not interfere with antibody response to influenza vaccine 2
- Common side effects include nausea (NNTH=25) and headaches (NNTH=32) 5
- To minimize gastrointestinal side effects, oseltamivir can be taken with food 1, 6
- Prophylaxis should be considered for unvaccinated persons who have frequent contact with high-risk individuals during community outbreaks 2
- Dose adjustment is required for patients with renal impairment 1
Special Populations
- For pregnant women and immunocompromised patients, the benefits of prophylaxis typically outweigh the risks when there is significant exposure 2
- Children receiving influenza vaccine for the first time may require 6 weeks of prophylaxis (4 weeks after first dose and 2 weeks after second dose) 2
By following these evidence-based recommendations for oseltamivir prophylaxis, the risk of influenza transmission within households and among close contacts can be significantly reduced, preventing illness and potential complications.