GENEVA - The World Health Organization said on Thursday it was looking into an unpublished Canadian study indicating that a seasonal flu shot could increase the risk of catching the H1N1 virus.

Marie-Paule Kieny, director of the WHO's initiative for vaccine research, said no other researchers had presented similar findings and it could be a study bias, although the Canadian investigators were well known and capable.

The reason why this may be different in Canada and in this particular study than in other places of the world is not yet identified. It may be a study bias, it may be that something is real, Kieny told a teleconference from the WHO headquarters.

She said all drug manufacturers who produced seasonal influenza shots will be able to make H1N1 vaccine, for a total annual output of 3 billion doses. Health workers, who make up 2 percent of the world's population, should be a priority.

(Reporting by Stephanie Nebehay; editing by Andrew Dobbie)

Canada Medicine