Bird flu vaccine trial encouraging -study

LONDON, May 11 (Reuters) A trial of an experimental vaccine against the H5N1 bird flu virus shows it produced a good immune response in healthy volunteers, scientists said today.

The vaccine made by a Sanofi Pasteur, a unit of the French drug company Sanofi Aventis , is based on a modified strain of the H5N1 virus.

Researchers tested various formulations of the vaccine with and without an adjuvant, an additive that can increase effectiveness.

They found two 30 microgram doses with an adjuvant induced the highest antibody response after 42 days.

''The vaccine that we tested appeared to be safe and well-tolerated and we did see a good immune response, in particular in one of the doses tested,'' said Dr Melanie Saville, of Sanofi Pasteur who headed the trial team.

She added that the results, reported online by The Lancet medical journal, were quite encouraging but further research was needed.

In an earlier trial, a vaccine made by Sanofi produced a satisfactory immune response at two doses of 90 micrograms. The dosage is important because the less vaccine needed, the more people can be vaccinated in the event of a pandemic.

DOSE-SPARING STRATEGIES About 300 million doses of human flu vaccines are produced a year at current production capacity. Increasing production could take years and require major investments, so dose-sparing strategies to stretch supplies are important.

Scientists fear the H5N1 bird flu virus that has spread from Asia to Europe, the West Asia and Africa could mutate into a highly infectious strain that could spark a pandemic with the potential for killing millions of people.

Companies are racing to develop pre-pandemic H5N1 vaccines that could save lives and buy time to develop a vaccine against a pandemic strain. It could take from four to six months from the start of a pandemic before a specific vaccine will be ready.

Volunteers in the study received the two doses of the vaccine 21 days apart.

All the vaccine formulations induced an immune reaction but the biggest was in people receiving the highest dosage, 30 micrograms, with an adjuvant. The adjuvant did not improve the response to lower doses of 7.5 and 15 micrograms.

''We will be moving into Phase 2 (trials) very shortly,'' Saville told Reuters.

She added that the findings will be submitted to European healthcare regulators as part of its ''mock up'' dossier. The process is expected to reduce the time necessary for approval of a pandemic vaccine.

GlaxoSmithKline Plc has started clinical trials of two vaccines against the H5N1 virus. Chiron Corp, is also working on a vaccine.

REUTERS SRS RN1322