The vaccine, ACAM-FLU-A, has been designed to target all 'A' strains of the flu virus - historically the strains that have been responsible for influenza pandemics. As such, the vaccine could have potential both as a universal pandemic flu vaccine and as part of a universal seasonal vaccine.

The Phase I trial will be based in the US, and will assess the vaccine's safety, tolerability and ability to stimulate an immune response, and will also evaluate the use of two adjuvants (the widely used adjuvant aluminium hydroxide, and Antigenics' QS-21 Stimulon, shown to be effective in other vaccine clinical trials).

A universal vaccine is widely seen as Holy Grail of influenza vaccines, able to target both pandemic and seasonal strains, and help ease the annual rush to re-engineer and manufacture sufficient supplies to handle the annual flu season.

By concentrating on a section of the flu virus that remains constant in all A strains, Acambis hopes that its vaccine could help overcome these difficulties.

Acambis' vaccine focuses on the M2 protein of the influenza A virus, the extracellular part (M2e) of which is highly conserved in all A strains. The conserved M2e domain is then genetically fused to a Hepatitis B virus core protein (HBc) and manufactured using E.Coli bacteria.

Pre-clinical data has shown that the vaccine induces anti-M2e antibodies, which protect against A strains in challenge models. According to research carried out by scientists at the University of Ghent, intraperitoneal or intranasal administration of the purified particles to mice provided 90-100 per cent protection against a lethal virus challenge.

According to Acambis, its universal vaccine could offer significant advantages over existing flu vaccines, eliminating some of the key hurdles currently hampering public health measures that aim to protect against the annual flu threat.

By targeting a conserved component of A strains, the vaccine would not need to be changed each year in response to the regular mutations in the flu virus. This offers major benefits in terms of being able to stockpile vaccines and manufacture at any time of the year, simultaneously doing away with the annual rush to produce enough vaccine doses for the flu season and the associated six-month delay between identifying the guilty mutation and a suitable vaccine becoming available.

The vaccine could also provide multi-year protection, and uses an efficient manufacturing process in E.Coli that produces high yields and is commercially scalable.

ACAM-FLU-A is the first vaccine candidate being developed under Acambis' influenza programme, and preliminary data from the Phase I trial is expected towards the end of this year.

Other projects that come under the umbrella of the influenza programme include efforts to identify a similar 'conserved' region within B strains of the influenza virus, in order to try and come up with a universal vaccine that will fight against the strains that cause the high morbidity associated with seasonal flu.

In addition to this the company is also investigating recombinant neuraminidase- and haemagglutinin-based vaccines and their delivery to develop seasonal vaccine candidates superior to existing flu vaccines.

With the market for influenza vaccines projected to hit $4bn (€3bn) by 2010 according to the company, and the World Health Organization repeatedly warning about the shortfall in global production capacity and the threat of pandemics, it is unsurprising that many companies are chasing after the elusive universal vaccine trophy.

However, Acambis is cautious, and while admitting that a universal vaccine approach could indeed have "a very strong competitive position," is reluctant to speculate as to how significant an impact its own product could have on the flu vaccine market.