Polio outbreak hits Nigeria

2007-10-08 15:20

Maria Cheng

London - For doctors struggling to eradicate polio, fighting the paralytic disease can mean vaccinating children in war-torn regions, persuading governments to pay attention, and begging donors for money.

A recent polio outbreak in Nigeria revealed another potential problem: the vaccine commonly used against it.

Last week, the World Health Organisation and the United States Centres for Disease Control reported that since 2005, 69 Nigerian children had been paralysed by a polio virus derived from the oral vaccine. Two other cases made it to Niger.

Such cases were not unknown, but the continuing Nigerian outbreak was the biggest ever, and followed a boycott of the vaccination campaign in Africa's most populous country because of unfounded fears that the vaccine was a Western plot to sterilise Muslims.

Officials now worried that the latest Nigerian outbreak traced to the vaccine could trigger another vaccine scare.

39% of children 'protected'

Olen Kew, a virologist at the US' Centres for Disease Control and Prevention, said: "This is the oral polio vaccine paradox. This vaccine is the most effective tool we have against the virus, but it's like fighting fire with fire."

What's needed to stop Nigeria's outbreak was more of the same vaccine that caused it.

Experts said these types of outbreaks only happened when not enough children were vaccinated. In northern Nigeria, only about 39% of children were fully protected against polio.

The oral polio vaccine contained a weakened version of polio virus. In rare instances, the virus could mutate into a form that was dangerous enough to spark new outbreaks.

Having lots of susceptible children to circulate among gives the virus a better chance of transforming into a deadlier strain.

In the West, an injectable polio vaccine with inactivated virus was used, to avoid the problems with the oral vaccine. But the oral vaccine used in the developing world was much cheaper than the injectable vaccine, and could be given to children by volunteers with little training.

The polio vaccine had previously ignited outbreaks in Haiti, the Dominican Republic, the Philippines, Madagascar, China and Indonesia.

Explosion of polio

In Nigeria, there was the added problem that "this is coming in the wake of all the other problems they've had in Nigeria", said Dr Donald A Henderson, who led WHO's smallpox eradication campaign in the 1970s.

In 2003, politicians in northern Nigeria cancelled vaccination campaigns for nearly a year, claiming the vaccine was a Western plot to sterilise Muslims. That led to an explosion of polio, and the virus jumped to approximately two dozen countries worldwide.

Now, health officials' decision to keep quiet about the outbreak linked to the vaccine for so long - WHO and CDC had known about the Nigerian outbreak since last year - might look suspicious.

Dr David Heymann, WHO's top polio official, said that because WHO considered the Nigerian outbreak to be an "operational" issue, it was unnecessary to share the information beyond its scientific committees.

CDC's Kew said added: "The people who are against immunisation may seize on anything that could strengthen their position, even if it's scientifically untenable."

Rumours were still rife among Nigerians that the vaccine was unsafe, and several religious leaders continued to lecture on its dangers. If there was another mass vaccine boycott that unleashed the virus further, that could derail the global eradication effort for good.

Nigerian health officials contacted by AP declined to comment on the situation.

- AP