The immunity has been granted for those involved in the preparation of reference strains, and the manufacturing, testing, development and distribution of vaccines.
The liability protection has been put in place in for measures to protect against the threat of a pandemic, based on the fact that "there is a credible risk that the spread of avian influenza viruses and resulting disease could in the future constitute a public health emergency."
The move comes in a bid to encourage the design, development and clinical testing of possible vaccines and medical treatments to protect the population in the case of an influenza pandemic.
The pandemic countermeasures come under the Public Readiness and Emergency Preparedness Act of 2005, and these amendments apply from December 1, 2006 through to February 28, 2010.
Last month the US HHS announced that it had awarded contracts to three vaccine manufacturers totalling $132.5m for the advanced development of influenza vaccines to protect against the H5N1 virus responsible for avian flu.
The contracts are to research vaccines using adjuvants to boost the body's immune response to the vaccine's active ingredient. The motivation for the emphasis on the development of vaccines incorporating adjuvants is the hope that they will provide a way to extend a limited vaccine supply to a greater number of people.
Five-year contracts were awarded to GlaxoSmithKline and Novartis, and the HHS is funding IOMAI for 15 months through Phase I clinical trials of their vaccine candidate with a view to expanding the contract following their successful completion.
Earlier this week the President announced his budget proposal for the HHS for fiscal year 2008, which included $1.2bn to go towards pandemic flu preparedness efforts. Plans for the funds include increased vaccine production capacity and stockpiling, purchase of additional anti-virals, development of rapid diagnostic tests and enhancing rapid response capabilities.
The H5N1 strain of avian flu has spread to more than 40 countries, and has infected over 270 people across the world killing over 160. A fresh outbreak was reported at a turkey farm in the UK last week, although workers who had fallen ill after being at the site have tested negative for the disease.
Although currently primarily an animal disease, experts fear that the virus could mutate, acquiring the ability for sustained transmission among humans. This could potentially trigger a flu pandemic, which would have grave consequences for global public health and put millions of lives at risk.