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

Treatment of Influenza B in Pediatric Patients

Oseltamivir is the antiviral drug of choice for treating influenza B in children, and should be initiated as soon as possible without waiting for laboratory confirmation in hospitalized children, those with severe illness, or children at high risk for complications. 1, 2

When to Initiate Antiviral Treatment

Strongly recommended for:

• All hospitalized children with suspected or confirmed influenza B, regardless of vaccination status or time since symptom onset 1, 2
• Children with severe, complicated, or progressive illness 1
• Children under 2 years of age (high-risk group for complications) 1, 2
• Children with underlying medical conditions including asthma, chronic pulmonary disease, cardiovascular disease, immunosuppression, neurologic disorders, metabolic disorders including diabetes, or sickle cell disease 1
• Children receiving long-term aspirin therapy 1

May be considered for:

• Otherwise healthy children with uncomplicated influenza if treatment can be initiated within 48 hours of symptom onset 1, 2
• Children whose household contacts are younger than 6 months or have high-risk medical conditions 2

Timing of Treatment

Treatment should be started immediately upon clinical suspicion and should not be delayed while awaiting laboratory confirmation. 1, 2 The greatest benefit occurs when treatment begins within 48 hours of symptom onset 1, 2, but treatment initiated after 48 hours still provides benefit in children with moderate-to-severe or progressive disease and should be offered 1, 3. For hospitalized patients with severe influenza, treatment initiated up to 5 days after symptom onset has demonstrated mortality reduction 1, 3.

Oseltamivir Dosing for Influenza B

Treatment duration: 5 days for all age groups 1

Weight-based dosing for 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 for infants:

• 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 (dosing not FDA-approved but recommended by AAP):

• <38 weeks postmenstrual age: 1.0 mg/kg per dose twice daily 1
• 38-40 weeks postmenstrual age: 1.5 mg/kg per dose twice daily 1
• >40 weeks postmenstrual age: 3.0 mg/kg per dose twice daily 1

Formulation and Administration

Oseltamivir is available as capsules (30,45,75 mg) and oral suspension (6 mg/mL concentration in 60-mL bottle). 1 If commercial suspension is unavailable, capsules can be opened and mixed with simple syrup or Ora-Sweet SF by pharmacies to achieve 6 mg/mL concentration. 1

Alternative Antiviral Options

Zanamivir (inhaled): Acceptable alternative for children ≥7 years without chronic respiratory disease, though more difficult to administer. Dosing is 10 mg (two 5-mg inhalations) twice daily for 5 days. 1 Not recommended for patients with asthma or chronic obstructive pulmonary disease due to bronchospasm risk. 1, 4

Peramivir (intravenous): Single-dose option approved for children ≥6 months with acute uncomplicated influenza who have been symptomatic ≤2 days, but efficacy in hospitalized patients with serious influenza has not been established. 1 In retrospective studies, oseltamivir showed superior outcomes compared to peramivir for influenza A, while outcomes were similar for influenza B. 1

Clinical Effectiveness Specific to Influenza B

Important caveat: Oseltamivir may be less effective for influenza B than influenza A. 3, 5 Studies show that fever duration is longer in children with influenza B treated with oseltamivir compared to influenza A (2.4 days vs 1.8 days). 5 However, treatment still provides benefit and is recommended. 1, 2

Documented benefits in children:

• Reduces illness duration by 17.6 hours overall (29.9 hours when excluding asthmatic children) 1, 2
• Reduces otitis media risk by 34% 1, 2, 3
• Reduces hospitalization risk 2
• In hospitalized children, significantly reduces symptom intensity and duration of hospitalization 6

Adverse Effects

Vomiting is the most common side effect, occurring in approximately 15% of children (vs 9% with placebo). 1, 3 This is mild and transient, and less likely when oseltamivir is taken with food. 7 Diarrhea may occur in children <1 year of age. 1, 2 Despite reports from Japan, controlled trials and surveillance have failed to establish a link between oseltamivir and neuropsychiatric events. 1, 2

Diagnostic Testing Considerations

Influenza testing should be performed when results will impact clinical management (e.g., to inform antiviral initiation, avoid antibiotics, or distinguish from other respiratory viruses). 1 For hospitalized patients, molecular assays with high sensitivity and specificity (e.g., RT-PCR) should be used. 1 However, negative rapid antigen tests should not rule out influenza or delay treatment decisions due to low sensitivity. 2 Clinical judgment based on underlying conditions, disease severity, time since symptom onset, and local influenza activity should guide treatment decisions. 1, 2

Chemoprophylaxis

Oseltamivir is the preferred agent for post-exposure prophylaxis of influenza A and B. 1 Prophylaxis should only be used when initiated within 48 hours of exposure. 1 Dosing is once daily at the same weight-based amounts used for treatment, continued for 7 days after last exposure. 1, 3 Chemoprophylaxis is not a substitute for vaccination. 1

Critical Pitfalls to Avoid

• Do not delay treatment while awaiting laboratory confirmation in high-risk or severely ill children 1, 2
• Do not withhold treatment beyond 48 hours in children with moderate-to-severe or progressive disease, as delayed treatment still provides benefit 1, 3
• Do not use zanamivir in children with asthma or chronic respiratory disease due to bronchospasm risk 1, 4
• Do not use double-dose oseltamivir therapy, as no additional benefit has been demonstrated 1, 3
• Do not use amantadine or rimantadine, as high levels of resistance persist 2