GENEVA - Nigeria is fighting a rare outbreak of vaccine-derived polio after 69 children caught the paralysing disease from others who had already been immunised, the World Health Organisation said on Monday.
The cluster occurred when some of those who received the oral polio vaccine excreted a mutated form of the virus, which infected others who were not immunised. Polio spreads through faecal-oral contact and thrives in areas with poor sanitation.
Though such mutations are extremely rare, vaccine-derived polio virus has also spread in past years in Cambodia, Myanmar, Indonesia and other countries where immunisation campaigns did not reach enough of the at-risk community, WHO spokeswoman Sona Bari said.
She said the northern Nigerian outbreak showed a need for better coverage in the region, which has struggled in its fight against polio since local leaders halted vaccinations programmes for nearly a year from mid-2003 over vaccine safety concerns.
"In Nigeria it is yet another indicator that not enough children are being vaccinated," Bari said. "We need especially for parents to understand that the only way to protect their kids from this virus is to vaccinate them."
Children need multiple doses of the oral vaccine to develop full immunity to the incurable disease.
Some 545 people worldwide have suffered paralysis from polio since the start of 2007, compared to 1,353 at the same point last year. Most have been in the four countries that are still endemic for the virus: Nigeria, Pakistan, Afghanistan and India.
Six other countries including Chad, Angola and Niger have also had polio cases this year despite having previously stopped the spread of the disease.
Nigeria's last vaccine-derived polio case was reported in August, Bari said, noting the outbreak was considered ongoing but appeared to be slowing due to continued vaccination drives.
The WHO and its partners UNICEF, Rotary International and the U.S.-based Centers for Disease Control and Prevention have spent some $5 billion and nearly 20 years trying to destroy the disease that afflicted 350,000 people a year in 1988.
Bruce Aylward, director of the eradication campaign, said earlier this year that recent advances against polio in some of its most stubborn strongholds meant it may be possible to wipe it out worldwide by the end of 2009.
