UK-based company PowderMed has reported positive clinical results with a DNA-based vaccine against seasonal influenza, and now plans to press on with a Phase II programme involving annual and bird flu strains later this year.

This is the first time that a DNA vaccine has been shown to have protective efficacy against influenza, which the company attributes to its intracellular delivery approach. Earlier studies of DNA vaccination, relying on intramuscular delivery, have yielded disappointing results in humans despite encouraging data in animals.

The vaccine consisted of influenza virus DNA delivered using PowderMed’s needle-free injection device – PMED – and at the highest dose tested (4mcg) stimulated antibody levels in the blood considered to be protective against flu. The vaccine coats the DNA with microscopic gold particles that are shot through into skin cells.

The results of the Phase I study, reported in the journal Vaccine, “adds to the growing body of scientific evidence that PowderMed’s DNA vaccine and the PMED platform show promise to address the major healthcare challenge posed by influenza, particularly in the event of an avian flu or other pandemic outbreak,” according to the company’s chief executive Clive Dix.

Another key advantage of a DNA-based approach is that vaccines could be created far more quickly in response to a influenza pandemic to the current egg-based production techniques and even newer approaches based on cell culture that are due to start reaching the market in 2008, according to Datamonitor.

The plasmid DNA for PowderMed’s vaccine is produced using a bacterial fermentation process that could carve the production time down from nine months with egg-based systems to a matter of weeks. Moreover, if the strain of virus causing an influenza pandemic mutated, it would be relatively simple to isolate the new strain, get hold of its key DNA sequences and produce new vaccine.