The epidemiology of influenza in children

Effect of influenza treatment with oseltamivir on health outcome and costs in otherwise healthy children

OBJECTIVE

To evaluate the effect of treating children with influenza with oseltamivir on health outcomes and costs to healthcare payers.

PATIENTS AND DESIGN

Health outcome data from the oseltamivir paediatric clinical development programme plus data from the literature were used in an economic model developed to predict morbidity and mortality due to influenza and its specified complications. Published data on the cost of care in the UK were used to compare oseltamivir with usual care in children aged 1-12 and 1-5 years by estimating cost-effectiveness and cost-utility ratios.

RESULTS

Oseltamivir reduced median time to return to normal health and activity by almost 2 days (40% reduction, 67.1 vs 111.7 hours; p < 0.0001) versus placebo. In children aged 1-5 years, a 48% reduction (63.5 vs 121.3 hours; p = 0.0003) was observed. Oseltamivir-treated children who developed otitis media returned to normal health and activity 30% faster (99.6 vs 141.5 hours; p = 0.0517) than the placebo group. In the economic model, oseltamivir in the base-case analysis (assuming 60% diagnostic accuracy, full compliance, and 100% receive and start treatment within 48 hours, standard discounting according to the UK National Institute of Clinical Excellence guidelines) resulted in favourable cost-utility ratios in children aged both 1-12 and 1-5 years, with incremental cost-utility rates of £11 173/quality-adjusted life year (QALY) and oseltamivir being dominant compared with usual care, respectively (year of costing, 2002). Even in conservative scenarios, most cost-utility ratios remained <£30 000/QALY.

CONCLUSIONS

Oseltamivir is an effective treatment for children with influenza, allowing faster return to normal health and activity compared with usual care. From the healthcare payer perspective, oseltamivir is a potentially cost-effective strategy for otherwise healthy children.

Effect of school closure on the incidence of influenza among school-age children in Arizona

OBJECTIVE

We assessed the impact of school closures as a viable intervention in the event of an influenza pandemic.

METHODS

We evaluated the effect of scheduled, two-week winter break school closures during the 2004-2008 school years on the occurrence of influenza among children aged 5-17 years in Arizona.

RESULTS

We found a consistent pattern of benefit to school-age children during winter school closures when non-school-age children and adults experienced significant increases in influenza incidence, an increase not seen among school-age children. Quantitative analysis showed that school closures may prevent or delay as much as 42% of potential influenza cases among school-age children. In addition, the ratio of illness in school-age children as compared with adults and non-school-age children decreased significantly from before to during the same school closure periods.

CONCLUSION

This analysis provides evidence to suggest that school-age children may experience a slowing of influenza transmission during winter school closures compared with those not of school age. Federal, state, and local policy makers may consider these findings in their pandemic influenza and public health emergency preparedness planning efforts.

Zanamivir: an update of its use in influenza

Zanamivir is a potent competitive inhibitor of the neuraminidase glycoprotein, which is essential in the infective cycle of influenza A and B viruses. Zanamivir (10mg by inhalation via the Diskhaler twice daily, or 10mg inhaled plus 6.4mg intranasally two or four times daily, for 5 days) reduced the median time to alleviation of major influenza symptoms by up to 2.5 days compared with placebo. Significant reductions of 1 to 2.5 days versus placebo were observed with inhaled zanamivir in phase III trials involving otherwise healthy adults, high-risk patients or children aged 5 to 12 years. Accelerated return to normal activities, and reduced interference with sleep, consumption of relief medication and incidence of complications leading to antibacterial use were also observed with zanamivir. When used for prophylaxis, inhaled zanamivir 10 to 20 mg/day for 10 days to 4 weeks (plus 6.4 mg/day intranasally in one trial) prevented influenza A in 67% of recipients in a university community, significantly reduced the number of families with new cases of influenza compared with placebo or prevented new cases of influenza in long-term care facilities. The tolerability of inhaled or intranasal zanamivir was similar to that of placebo in otherwise healthy adults, high-risk and elderly patients, and children. Recommended dosages of zanamivir did not adversely affect pulmonary function in patients with respiratory disorders in a well-controlled trial, although there have been rare reports of bronchospasm and/or a decline in respiratory function.

CONCLUSION

Zanamivir (used within 48 hours of symptom development) reduces the duration of symptomatic illness, causes accelerated return to normal activities or reduces complications requiring antibacterial use in adults, high-risk individuals and children with influenza. Vaccination remains the intervention of choice for prophylaxis in selected populations. However, the efficacy, good tolerability profile and lack of resistance with zanamivir make it a useful option, particularly in those not covered or inadequately protected by vaccination, who are able to use the inhalation device. The use of zanamivir in patients with respiratory disorders remains unclear because of concerns regarding its potential for bronchospasm. Prospective cost-effectiveness analyses and investigations of efficacy in preventing serious complications of influenza, particularly in high-risk patients, are required. Zanamivir shows potential for prophylaxis in persons for whom vaccination is contraindicated or ineffective, in elderly or high-risk patients in long-term care facilities and in households.