The U.N. children's agency says six states in Nigeria's north have had at least 20 cases of polio this year.
Jacques Boyer, U.N. Children's Fund deputy country representative, spoke Tuesday at a meeting with religious and traditional leaders in the city of Kano.
He said Nigeria has seen a marked reduction in cases over the past few years from 338 cases in 2009 to a recorded 21 cases of polio in 2010. Boyer said the fight had gone too far to "relapse" now.
Polio is largely unknown in most of the world, but vaccines to protect children from paralysis and death have been met with resistance in Nigeria's impoverished north.
In 2003, imams led a boycott of vaccinations, saying they were a Western plot to make Muslims infertile or infect them with AIDS, but authorities have since worked with partners to gain their support.