Preliminary research with a different vaccine suggests that approach may work, Dr. Anthony Fauci, the National Institutes of Health's infectious disease chief, told a Senate panel Wednesday.

Senate Majority Leader Bill Frist, R-Tenn., also said lawmakers should pass legislation by Thanksgiving to fund preparations for a possible worldwide outbreak of bird flu.

Immune-Boosting Chemical

US health officials have hired two companies, Sanofi-Aventis and Chiron Corp., to produce $162.5 million worth of vaccine against the virulent H5N1 bird flu, the strain that has killed at least 63 people in Southeast Asia since 2003. The US government hopes eventually to stockpile enough H5N1 vaccine for 20 million people.

But a major barrier is that it requires two huge doses of the H5N1 vaccine to produce a protective immune response.

Chiron recently paired an experimental vaccine against another bird-flu strain, H9N2, with an immune-boosting chemical called an adjuvant. Preliminary testing, funded by NIH, in 96 people showed that adding the adjuvant lowered the required vaccine dose, results that Fauci called encouraging.