Dutch biotechnology company Crucell has joined the ranks of companies seeking to develop vaccines against avian influenza, starting a trial of three versions of a candidate targetted against the H9N2 strain of bird flu.

While most of its larger vaccine rivals – including Sanofi-Aventis, GlaxoSmithKline and Novartis (via Chiron) – are concentrating on the H5N1 strain of bird flu as the most likely to cause a pandemic in humans, other strains, including H9 and H7 have also caused lethal outbreaks among birds in the past.

Crucell also intends to develop vaccine candidates against the H5N1 strain, and said this preliminary testing on H9N2 would help plan that programme.

The trial will be performed in collaboration with a team based in Leicester, UK, and will involve 560 healthy adults who will receive either a non-adjuvanted whole virion vaccine, an alum-adjuvanted whole virion vaccine and a virosomal subunit vaccine, all based on the H9N2 virus. The whole virion vaccine will be administered by both intramuscular and intradermal routes, with the latter of particular interest as it may allow a lower dose of antigen to be used, and so allow supplies to stretch farther in the event of a pandemic.

Crucell said it expects to have the results of its testing by the end of the year, noting that trials of this type can be used in support of a "pandemic core dossier", which forms the basis for rapid approval by the regulatory authority of a vaccine against an actual pandemic threat once it emerges.