What is the recommended treatment for pediatric patients with influenza B (flu B)?

Treatment of Influenza B in Pediatric Patients

Oseltamivir (Tamiflu) is the antiviral drug of choice for treating influenza B in children, and should be initiated as soon as possible—ideally within 48 hours of symptom onset—for all hospitalized children, those with severe illness, and high-risk patients, though treatment beyond 48 hours still provides benefit and should not be withheld. 1, 2

Who Should Receive Antiviral Treatment

High-Priority Groups (Treat Immediately):

• All hospitalized children with suspected or confirmed influenza B, regardless of vaccination status or time since symptom onset 1, 2, 3
• Children with severe, complicated, or progressive illness (pneumonia, respiratory failure, encephalopathy) 1, 2
• Children younger than 2 years of age, who are at increased risk for complications and hospitalization 1, 2, 3
• Children with underlying high-risk conditions including:
  • Chronic pulmonary disease (including asthma) 1
  • Cardiovascular disease 1
  • Immunosuppression 1
  • Neurologic and neurodevelopmental conditions 1
  • Metabolic disorders including diabetes 1
  • Chronic renal or hepatic disease 1

Consider Treatment For:

• Otherwise healthy children with influenza when treatment can be initiated within 48 hours, especially if a decrease in symptom duration is desired 2, 3
• Children whose siblings or household contacts are younger than 6 months or have high-risk conditions 1, 2, 3

Oseltamivir Dosing for Influenza B

Standard Treatment Duration: 5 days 1, 2

Weight-Based Dosing (Children ≥12 months):

• ≤15 kg: 30 mg twice daily 1, 2
• >15-23 kg: 45 mg twice daily 1, 2
• >23-40 kg: 60 mg twice daily 1, 2
• >40 kg: 75 mg twice daily 1, 2

Age-Based Dosing (Infants <12 months):

• 9-11 months: 3.5 mg/kg per dose twice daily 1, 2
• 0-8 months (term infants): 3 mg/kg per dose twice daily 1, 2

Preterm Infants:

• <38 weeks postmenstrual age (PMA): 1 mg/kg per dose twice daily 1
• 38-40 weeks PMA: 1.5 mg/kg per dose twice daily 1
• >40 weeks PMA: 3 mg/kg per dose twice daily 1

Note: The FDA has approved oseltamivir for children as young as 2 weeks of age 3, 4. The AAP supports use in both term and preterm infants from birth, as benefits likely outweigh risks 1, 3.

Timing and Clinical Decision-Making

Critical Timing Considerations:

• Treatment should be started as soon as possible after illness onset and should not be delayed while waiting for laboratory confirmation 1, 2
• Greatest benefit occurs when initiated within 48 hours of symptom onset 2, 3
• However, treatment after 48 hours in children with moderate-to-severe or progressive disease has shown benefit and should still be offered 1, 3
• For hospitalized children and those with severe illness, treatment is recommended regardless of illness duration 1, 2

Diagnostic Testing:

• Molecular assays (RT-PCR) with high sensitivity and specificity should be used for hospitalized patients when influenza is suspected 1, 2
• Rapid antigen tests have lower sensitivity and negative results should not rule out influenza or delay treatment decisions 2
• Clinical judgment based on underlying conditions, disease severity, time since symptom onset, and local influenza activity should guide treatment decisions 1, 2

Expected Benefits

Clinical Effectiveness:

• Reduces duration of illness by approximately 17.6 to 36 hours (26%) 1, 2
• Reduces risk of otitis media by 34% 1, 2
• Decreases hospitalization rates and need for subsequent antibiotics 5
• In hospitalized children, early oseltamivir is associated with shorter hospital length of stay, lower odds of ICU transfer, and reduced mortality 6
• In critically ill patients, treatment reduces estimated risk of death (odds ratio 0.36) 1

Adverse Effects and Safety

Common Side Effects:

• Vomiting is the most common adverse effect, occurring in approximately 15% of treated children versus 9% receiving placebo 1, 2, 3
• Nausea and headache 1
• Diarrhea may occur in children <1 year of age 1, 2

Important Safety Information:

• Taking oseltamivir with food reduces gastrointestinal side effects 5
• Despite reports from Japan, controlled clinical trials and ongoing surveillance have failed to establish a link between oseltamivir and neuropsychiatric events 1, 3
• Standard-dose therapy is recommended; double-dose therapy has not shown additional benefit 1, 3

Formulation and Administration

Oseltamivir is available in:

• Capsules: 30 mg, 45 mg, and 75 mg 1
• Oral suspension: 6 mg/mL concentration in 60-mL bottle 1, 2
• If commercial suspension is unavailable, capsules may be opened and contents mixed with simple syrup or Ora-Sweet SF (sugar free) to a final concentration of 6 mg/mL 1

Alternative Antiviral Agents (Less Preferred for Influenza B)

Zanamivir (inhaled):

• Acceptable alternative for patients ≥7 years without chronic respiratory disease 1
• Dose: 10 mg (two 5-mg inhalations) twice daily for 5 days 1
• More difficult to administer and requires proper inhaler technique 1
• Not recommended for patients with asthma or chronic obstructive pulmonary disease due to risk of bronchospasm 1, 7

Peramivir (IV):

• Approved for acute uncomplicated influenza in children ≥6 months who have been symptomatic for no more than 2 days 1
• Efficacy in hospitalized patients with serious influenza has not been established 1
• In children with influenza B, peramivir showed similar clinical outcomes to oseltamivir 1

Baloxavir marboxil:

• Approved for otherwise healthy patients ≥5 years with acute uncomplicated influenza 1
• Less cumulative pediatric experience compared to oseltamivir 1

Common Pitfalls to Avoid

• Do not delay treatment while waiting for laboratory confirmation in high-risk or severely ill children 1, 2
• Do not withhold treatment if >48 hours have passed since symptom onset in children with moderate-to-severe or progressive disease 1, 3
• Do not rely on rapid antigen tests to rule out influenza due to low sensitivity; use molecular assays when possible 1, 2
• Do not use amantadine or rimantadine due to high resistance rates 5
• Do not use double-dose oseltamivir; standard dosing is recommended 1, 3

Prophylaxis Considerations

Post-Exposure Prophylaxis:

• Oseltamivir is the preferred agent for post-exposure prophylaxis of influenza A and B 1
• Should only be used when initiated within 48 hours of exposure 1
• Dose: Same weight-based dosing as treatment, but given once daily for 7 days 1
• Consider for high-risk household contacts of infected children 2
• Not a substitute for vaccination 1