KANO, Nigeria -- Sticking to its position that the polio vaccine represents a U.S. plot against Muslims, an overwhelmingly Islamic northern Nigerian state declared it would boycott an emergency immunization campaign being launched to stop the crippling outbreak that is spreading across west and central Africa. The announcement from Kano state came on the eve of a World Health Organization campaign to immunize 63 million children in 10 African nations as the polio outbreak spreads from northern Nigeria into countries where the disease had been eradicated.