Oseltamivir utilization during the 2009 H1N1 influenza pandemic, Taiwan

Background
A global pandemic of novel influenza A/H1N1 emerged from Mexico and US in March 2009. Antiviral medications are recommended to treat suspected or confirmed influenza patients, especially in those with high risk for morbidity and mortality. Influenza rapid test and oseltamivir were paid by National Health Insurance （NHI） and widely used during the influenza pandemic in Taiwan. The trends of prescription in specific age group and geographic difference are of particular interest.

Material and Method
The study collected all influenza rapid test and oseltamivir prescription from NHI claims database in 2009. Rates of oseltamivir prescription in different age groups and regions are calculated using population data from Taiwan Statistical Yearbook of Interior. The trend of prescription was compared with measures of influenza virus activity from Taiwan Centers for Disease Control.
Results
There were 1,559,233 influenza rapid test conducted and 516,772 courses of oseltamivir prescriptions from NHI claims database in 2009. Less than 0.1% of oseltamivir were prescribed before August. Both peaks of oseltamivir and rapid test prescriptions were seen in week 48, which were compatible with the trend of influenza virus activity. School-aged children had the highest oseltamivir prescription rate, followed by adolescents and pre-school-aged children. The prescription rate in Taipei region peaked in week 44, which is earlier than other regions. Generally, oseltamivir prescription rate is low in southern Taiwan.
Conclusions
The trends of influenza rapid test and oseltamivir prescription were closely realted to the level of influenza virus activity. Oseltamivir prescription rate is high among persons aged under 18 years, who are at high risk of 2009 H1N1 influenza infection.