London School of Hygiene & Tropical Medicine

The most thorough analysis of oseltamivir (marketed as Tamiflu) data to date, including all available published and unpublished randomised treatment trials of adults, suggests that the antiviral drug shortens the duration of flu symptoms by about a day, compared to placebo, in adults with laboratory-confirmed influenza.

The results, published in The Lancet, also indicate that oseltamivir significantly reduces the risk of influenza complications requiring antibiotics (such as pneumonia) and hospitalisations in adults infected with influenza.

For the first time, the meta-analysis includes individual patient data from all published and unpublished trials (made available by the manufacturer Roche). The study was conducted by Professor Stuart Pocock and Joanna Dobson at the London School of Hygiene & Tropical Medicine, working with partners at the University of Michigan School of Public Health and the University of Alabama at Birmingham in the US.

The authors analysed data from nine trials comparing the licensed 75mg dose of oseltamivir with placebo for the treatment of seasonal influenza in 4328 adults between 1997 and 2001.

They found that treating adults with laboratory-confirmed influenza with oseltamivir reduced the duration of symptoms by 21% compared with placebo (from 123 hours to 98 hours). However, no benefit was noted in adults without influenza virus infection. 

The analysis confirmed that oseltamivir treatment results in a significantly increased risk of nausea (absolute increase 3.7%) and vomiting (4.7%) compared with placebo. The authors noted no difference between the groups in neurological and psychological disorders in this setting, which have previously been linked with the drug.

Although rates of complications were low, oseltamivir reduced the risk of lower respiratory tract infections requiring antibiotics more than 48 hours after study entry by 44% compared with placebo (4.9% vs 8.7%), and hospital admission for any cause by 63% (0.6% vs 1.7%) in adults with laboratory-confirmed influenza.

According to the authors: "The safety and effectiveness of oseltamivir has been hotly debated, with some researchers claiming there is little evidence that oseltamivir works. Our meta-analysis provides compelling evidence that oseltamivir therapy reduces by one day the typical length of illness in adults infected with influenza and also prevents complications and reduces the number of people needing hospital treatment. Whether the magnitude of these benefits outweigh the harms of nausea and vomiting needs careful consideration."

The study was funded by the Multiparty Group for Advice on Science (MUGAS) foundation.

Publication

• Joanna Dobson, Richard J Whitley, Stuart Pocock, Arnold S Monto. Oseltamivir treatment for influenza in adults: a meta-analysis of randomised controlled trials. The Lancet. DOI: 10.1016/S0140-6736(14)62449-1