Treatment with the antiviral medication Tamiflu (oseltamivir phosphate) significantly reduced the risk of pneumonia in patients diagnosed with flu, according to a new retrospective cohort study of over 70,000 Americans.
Reduction in pneumonia incidence was most pronounced in higher-risk groups, with a 59 percent decrease in older Americans, and a 66 percent decrease in children 12 and under. The study was presented Sunday at the InterScience Congress on Antimicrobial Agents & Chemotherapy (ICAAC) in Washington, DC.
Using a database of medical and prescription claims, researchers analyzed patients who had received a flu diagnosis during one or more seasons between 1999 and 2002. Outcomes in patients treated with Tamiflu were compared to those who had not been treated with any antiviral medication for three months prior to flu diagnosis. An analysis of three age groups, aged one and over, found:
- In patients age one - twelve, risk of pneumonia was reduced by 66 percent
- Patients 60 years and older saw a reduction of 59 percent
- In 13 - 59 year olds, risk of pneumonia was reduced by 19 percent
"The results are a significant step in understanding a potential role for Tamiflu in reducing risk of pneumonia and other sequelae of influenza," said Dominick Iacuzio, PhD, Medical Director of Roche, which commissioned the study and markets Tamiflu, a prescription antiviral approved for the prevention and treatment of influenza. "Based on these findings, Roche is investing in two additional studies to further explore this therapeutic area."
Researchers measured pneumonia incidence by claims diagnosis, dispensing of an antibiotic, or hospitalization within 30 days after a flu diagnosis. In some age groups, treatment with Tamiflu also decreased incidence of antibiotic dispensing and hospitalization, though not all comparisons reach the same level of significance.
Investigators analyzed each age group separately, and accounted for numerous baseline variables using Cox proportional hazards models.
A study published in the September 15, 2004 issue of the Journal of the American Medical Association found that more than 200,000 people are hospitalized each year because of flu-related illnesses, far more than the 114,000 annual hospitalizations previously estimated. Flu complications are more severe in people over 50 and the highest rates of hospitalizations are found in people over 85. The study also found that children under five are hospitalized at higher rates than those in the 50-64 age group. According to the U.S. Centers for Disease Control (CDC), an average of 36,000 people in the United States die from influenza each year.
While most people recover from the flu without problems, the illness can sometimes lead to serious complications, most commonly pneumonia. Pneumonia is a common illness that affects millions of people each year in the U.S. and can range from mild to severe, even fatal. The CDC cites more than 64,000 deaths from pneumonia in 2002. Most deaths occur in those who are older or whose immune systems are not working properly. Pneumonia can be caused by bacteria, viruses and fungi. Viruses including influenza A, are the second leading cause of pneumonia.