The World Health Organization says Kano, an Islamic State in northern Nigeria, has begun training health workers in preparation for a polio immunization campaign it hopes to begin next month, following a delay caused by controversy over the vaccine. U.N. agencies hope to immunize about 3.5 million children under age five, using a vaccine manufactured in Indonesia.

The governor of Kano has told the World Health Organization he believes the polio vaccine is safe and wants to resume polio immunizations in July. The head of WHO's Global Polio Eradication Campaign, David Heymann, says extraordinary measures are being taken to prepare for the campaign, which could take place in two weeks at the earliest.

He says United Nations agencies, at the request of Kano officials, are helping to train health workers and inform the public about the importance of immunizing their children. He says WHO has increased its staff in Kano and UNICEF has stockpiled millions of doses of polio vaccine in the area.

But, Dr. Heymann warns the campaign could be put on hold if any one of several independent committees advising the government on polio decides against it. This would be unfortunate, he says, because there is still time to stop polio transmission by the end of this year.

"We are working towards that target and if things unblock in Kano, as we believe they are, we believe that there is a chance that they could interrupt transmission through high quality immunization campaigns if they can ensure high quality over the next six months," said Dr. Heymann. "The same is true for West Africa, if the campaigns in West Africa can be conducted. If we receive the resources we need to do those campaigns, we believe that they also can interrupt transmission which might have been set up because of the upcoming outbreak."

Kano suspended immunizations last year on the basis of false rumors that the polio vaccine causes infertility and AIDS. As a result, WHO says, 259 children in Nigeria, mainly in Kano have become paralyzed with polio and the virus has spread to 10 previously polio-free countries across Africa.

Dr. Heymann says Kano is the key to global efforts to eradicate polio, an effort which has been underway for 20 years and cost $3 billion.

WHO warns international travelers to northern Nigeria to make sure they are fully immunized against polio.