What is the recommended treatment for influenza B in an otherwise healthy 14‑year‑old adolescent?

Treatment for Influenza B in a 14-Year-Old

Start oseltamivir 75 mg orally twice daily for 5 days immediately, ideally within 48 hours of symptom onset, regardless of vaccination status. 1, 2, 3

Recommended Antiviral Treatment

Oseltamivir (Tamiflu) is the drug of choice for treating influenza B in adolescents. 1, 2, 3 The American Academy of Pediatrics recommends oral oseltamivir as the preferred antiviral agent for managing influenza infections in children and adolescents, available in both capsule and oral suspension formulations. 1, 2

Dosing for a 14-Year-Old

• 75 mg orally twice daily for 5 days (standard adult/adolescent dose for patients ≥13 years) 1, 4, 3
• Can be taken with or without food, though taking with food may reduce gastrointestinal side effects 1, 3
• Complete the full 5-day course even if symptoms improve earlier 4

Timing Is Critical

Initiate treatment as soon as possible within 48 hours of symptom onset for maximum benefit. 1, 2 The greatest effect on outcomes occurs when treatment begins within this window, reducing illness duration by approximately 1–1.5 days. 1, 4 However, treatment should not be delayed while waiting for confirmatory influenza test results—clinical judgment based on symptoms and local influenza activity should guide immediate treatment decisions. 1, 2

When to Treat Beyond 48 Hours

For an otherwise healthy 14-year-old who presents beyond 48 hours, treatment may still be considered if:

• The adolescent has severe or progressive illness 1, 2
• There are household contacts who are high-risk (infants <6 months, elderly, immunocompromised) 1
• The patient has any underlying chronic medical conditions 1

For a previously healthy adolescent with mild illness presenting after 48 hours, supportive care alone is appropriate. 4

Expected Clinical Benefits

When started within 48 hours, oseltamivir provides:

• Reduction in illness duration by 17.6–36 hours (approximately 1–1.5 days) 1, 4
• Faster return to normal activities 1, 4
• Reduced risk of complications, including a 34% lower risk of otitis media and 50% lower risk of pneumonia 1, 4
• Decreased antibiotic use by approximately 10% 2

Important Caveat About Influenza B

Oseltamivir may be somewhat less effective against influenza B compared to influenza A. 1, 4 Studies show oseltamivir reduces illness duration in influenza B from 173.9 to 110.0 hours (p=0.03), though the effect is less pronounced than with influenza A (34% reduction vs. 8.5% reduction in time to symptom resolution). 1, 4 Despite this difference, the American Academy of Pediatrics still recommends treatment, as oseltamivir has demonstrated activity against influenza B viruses. 1

Common Side Effects and Safety

Vomiting is the most common adverse effect, occurring in approximately 5–15% of treated patients compared to 9% with placebo. 1, 4 This is generally mild, transient, and rarely leads to discontinuation. 1, 4 Taking oseltamivir with food can reduce nausea and vomiting. 1, 3

Despite historical concerns, controlled clinical trials and ongoing surveillance have failed to establish a link between oseltamivir and neuropsychiatric events. 1, 4

Alternative Agents

Inhaled zanamivir is an acceptable alternative for adolescents ≥7 years who do not have chronic respiratory disease, though it is more difficult to administer via the special inhaler device. 1, 5 Zanamivir appears equally effective against both influenza A and B. 6, 5

Critical Pitfalls to Avoid

• Do not wait for laboratory confirmation before starting treatment in symptomatic adolescents during flu season, especially if within 48 hours of symptom onset 1, 2
• Do not rely on negative rapid antigen tests to rule out influenza or make treatment decisions, as these tests have poor sensitivity 1, 2
• Do not withhold treatment based solely on vaccination status—vaccinated individuals can still develop influenza and benefit from antiviral therapy 1, 2

Supportive Care

In addition to antiviral therapy, provide:

• Adequate hydration 1
• Antipyretics for fever (acetaminophen or ibuprofen; avoid aspirin in adolescents due to Reye's syndrome risk)
• Rest and symptomatic relief

Household Contact Considerations

If the 14-year-old lives with high-risk household contacts (infants <6 months, elderly, immunocompromised individuals), those contacts should be offered post-exposure prophylaxis with oseltamivir 75 mg once daily for 10 days if exposure occurred within 48 hours. 1, 4

Important Reminder

Antiviral treatment is not a substitute for annual influenza vaccination, which remains the primary prevention strategy. 1, 2, 3 The adolescent should receive annual influenza vaccination as recommended by the CDC Advisory Committee on Immunization Practices. 3