What is the recommended treatment for influenza in infants?

Treatment of Influenza in Infants

Oseltamivir is the recommended antiviral treatment for influenza in infants, with FDA approval for use starting at 2 weeks of age, and should be initiated as soon as possible regardless of time since symptom onset in hospitalized infants or those at high risk for complications. 1

Who Should Receive Treatment

All infants with suspected or confirmed influenza should be offered antiviral treatment given their high risk for complications, including:

• All hospitalized infants with suspected influenza 1, 2
• Infants with severe, complicated, or progressive illness 1
• Any infant under 2 years of age, as they are at increased risk of hospitalization and complications 1
• Treatment should be offered even if more than 48 hours have passed since symptom onset, as infants remain high-risk 1

Medication and Dosing

Oseltamivir (oral suspension, 6 mg/mL concentration) is the drug of choice for infants: 1

Age-Based Dosing for Treatment (5 days duration):

• Term infants 0-8 months: 3 mg/kg per dose twice daily 1
• Infants 9-11 months: 3.5 mg/kg per dose twice daily 1
• Infants ≥12 months:
  • ≤15 kg: 30 mg twice daily 1

  • 15-23 kg: 45 mg twice daily 1

Special Populations:

Preterm infants require adjusted dosing based on postmenstrual age (gestational age + chronological age): 1

• <38 weeks postmenstrual age: 1 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 mg/kg per dose twice daily 1

For extremely preterm infants (<28 weeks), consult pediatric infectious disease specialist 1

Timing of Treatment

Treatment should be initiated immediately upon clinical suspicion without waiting for confirmatory testing: 1, 2

• Greatest benefit occurs when started within 48 hours of symptom onset 1, 2
• However, treatment after 48 hours still provides benefit in infants and should be strongly offered given their high-risk status 1
• Early treatment (within 12-24 hours) in infants 1-3 years reduced acute otitis media by 85% and shortened illness duration by 3.5 days 3

Clinical Efficacy in Infants

Oseltamivir demonstrates substantial clinical benefit in the infant population:

• In infants <1 year with influenza A, treatment shortened mean illness duration from 253.5 hours to 82.1 hours (P=0.0003) 4
• For influenza B, duration decreased from 173.9 to 110.0 hours (P=0.03) 4
• Fever resolved within 36 hours in 82% of treated infants <1 year 5
• Viral load declined rapidly within 1-2 days of treatment initiation 4
• Reduces risk of complications including hospitalization and death 1

Administration and Formulation

Oseltamivir can be administered without regard to meals, though giving with food may improve gastrointestinal tolerability: 1, 6

• Available as commercially manufactured oral suspension (6 mg/mL) 1
• If commercial suspension unavailable, capsules can be opened and mixed with simple syrup or Ora-Sweet SF by pharmacies to achieve 6 mg/mL concentration 1

Common Adverse Effects

Vomiting is the most common adverse effect, occurring in approximately 5-15% of treated children: 1, 2

• Diarrhea may occur in children <1 year of age 1, 2
• In infants <1 year, 50% experienced additional symptoms during treatment, most commonly mild gastrointestinal symptoms 5
• Most adverse events are mild in intensity 5, 7
• Despite reports from Japan, controlled trials and surveillance have failed to establish a link between oseltamivir and neuropsychiatric events 1, 2

Alternative Agents

Zanamivir is not recommended for infants:

• Only approved for children ≥7 years for treatment and ≥5 years for prophylaxis 1, 8
• Requires adequate inspiratory flow through inhalation device, which young children often cannot achieve 8
• Not recommended for patients with chronic respiratory disease due to bronchospasm risk 1, 8

Peramivir is only approved for children ≥2 years of age 1, 2

Antiviral Resistance

Current influenza strains show minimal resistance to oseltamivir:

• Among recent surveillance, <0.5% of influenza A (H3N2) and pH1N1 viruses showed oseltamivir resistance 1
• Amantadine and rimantadine should not be used due to high resistance levels 1, 2
• Continuous monitoring by CDC tracks resistance patterns 2

Critical Clinical Pitfalls

Do not delay treatment while awaiting confirmatory testing - clinical judgment based on symptoms and local influenza activity should guide immediate treatment decisions 1, 2

Do not withhold treatment beyond 48 hours - infants remain high-risk and benefit from treatment even when started later in illness course 1

Do not rely on rapid antigen tests to rule out influenza - these have low sensitivity and negative results should not prevent treatment in high-risk infants 1, 2

Ensure proper weight-based dosing - preterm infants require lower doses due to immature renal function and risk of excessive drug concentrations 1