By Richard Lenti
Disappointing results from this year’s flu vaccine has scientists around the world looking for more effective ways to fight influenza.
This week the U.S. Centers for Disease Control and Prevention (CDC) said the flu vaccine was effective in only 56 percent of people who got the shot, and largely failed to protect the elderly. The effectiveness of flu vaccines usually range from 50 to 70 percent, so this year’s vaccine is on the low end.
“We simply need a better vaccine against influenza, one that works better and lasts longer,” said CDC Director Dr. Thomas Frieden.
Researchers in Canada, Britain and Australia are working on a promising new antiviral drug – not a vaccine – that blocks the flu virus from spreading to other cells once a person becomes infected. Their research study is being published in the peer-reviewed journal Science Express.
There are currently only two antiviral drugs that can slow influenza’s progress. Relenza and Tamiflu both block a viral enzyme which helps the virus infect new cells, but they can only be administered up to two days after a person has been infected. Even though they are normally reserved for people at higher risk of complications, such as children or the elderly, resistance to Relenza and Tamiflu is growing because of their overuse.
The new class of drugs being developed by researchers – called DSFAs — bind to the neuraminidase enzyme on the surface of the flu virus which prevents it from replicating in healthy cells. Both Relenza and Tamiflu also work by attaching to this enzyme, but DFSAs do it in a way that the flu virus cannot become resistant to the drugs.
“Our drug agent uses the same approach as current flu treatments by preventing neuraminidase from cutting its ties with the infected cell,” said lead author Steve Withers from the University of British Columbia. ”But our agent latches onto this enzyme like a broken key, stuck in a lock, rendering it useless.”
When DFSAs were given to mice infected with a lethal amount of the flu virus, the drug prolonged their survival and formed a stronger type of bond with the neuraminidase enzyme than both Tamiflu and Relenza. More importantly, the drug was also effective against flu virus strains that are resistant to both of the current flu drugs.
“Our drug can work even better in drug resistant strains than in natural viruses emphasizing that it is working through a totally different mechanism,” said co-author Dr. Andrew Watts from the University of Bath.
Watts emphasizes that research into DFSAs is in its very early stages and more animal studies are needed before they can be tested on humans. It could be six to seven years before the new drug comes on the market.
The World Health Organization estimates that influenza affects three to five million people every year. Between 3,000 and 50,000 people in the U.S. die from influenza annually, depending on the severity of the flu season.