Independent research carried out in Nigeria has found no traces of HIV or anti-fertility agents in the polio vaccine being used there.
Nigeria has the highest rates of polio in the world
Immunisation campaigns in the northern states had almost stopped because of fears that the vaccine was unsafe.
The World Health Organisation said it hoped that immunisation schemes could now resume.
The polio virus has already spread from Nigeria to neighbouring countries which had been free of the disease.
The controversy over the safety of the oral polio vaccine started after some Islamic leaders alleged that it contained a contraceptive that would render children infertile, as part of a western plot to curb the Muslim population.
WHO maintains the vaccine is safe, saying it is made to the same high quality world-wide; but religious leaders demanded independent studies.
BBC health reporter Ania Lichtarowicz says the tests carried out at the National Hospital in Abuja and the Ahmadu Bello University Teaching Hospital were witnessed by representatives of WHO, religious leaders and state health officials.
They showed that a random sample of oral polio vaccines did not contain reproductive hormones that could affect fertility.
Nigeria's neighbours are at risk
The virus has now spread to six neighbouring countries - including Chad and Burkina Faso - which had previously been declared polio free.
Nigeria has the world's highest number of cases.
Poliomyelitis is an acute viral infection which mainly affects children and can be spread by simple physical contact.
It causes permanent paralysis and other forms of physical disability in many of its victims.