The northern Nigerian state of Kano has resumed polio vaccinations after an 11-month ban that threatened to undermine world efforts to eradicate the disease.
Nigeria is one of six countries where polio is endemic
The immunisation programme was halted last August because of fears by local Muslim scholars that vaccines were contaminated as part of a US plot.
Kano officials say they are satisfied that a new batch of vaccines are safe.
Nigeria now accounts for about 80% of new cases and 10 polio-free African nations have been reinfected.
Kano Governor Ibrahim Shekaru administered the oral vaccine to several babies at a ceremony in the village of Takai on Saturday, signalling his state's resumption of vaccinations.
He reassured parents that the vaccines imported from Indonesia were safe, underscoring his claim by publicly giving his own daughter a dose.
United Nations officials, who have voiced mounting concern over the past year, expressed relief as health workers began the door-to-door campaign which aims to reach four million children in the next few days.
"It's the beginning of the very final push to eradicate polio from Nigeria and the world," said Gerrit Beger, spokesman for the UN children's agency, Unicef.
"Polio will have no hiding place any more from today."
The mainly Muslim state withdrew from the polio campaign in August 2003 following reports by Islamic clerics that vaccines had been contaminated as part of an American plan to render Muslim women infertile.
Since then, the incidence of new cases has exploded, spreading from Kano across Nigeria, Africa's most populous country.
There are no exact figures but well over 200 new cases have been reported compared with fewer than 50 cases for the same period in the previous year.
Polio has also reappeared in 10 African nations, leading the World Health Organization (WHO) to warn that the region is facing an epidemic.
Last month, the WHO announced an emergency immunisation campaign of 74 million children across Africa to try to rescue its goal of wiping out polio worldwide by 2005.
Polio, which mainly affects children under five, is caused by a virus that invades the nervous system and can cause total paralysis or death.
The disease is considered endemic in only six countries - Afghanistan, Egypt, India, Niger, Nigeria, and Pakistan.
When the eradication drive was launched in 1988, polio was a serious problem in 125 countries.