Polio in Nigeria

30 October 2007

Recently there has been an outbreak of polio in Nigeria caused by vaccine-derived poliovirus, VDPV. This outbreak is not unusual except that it is the largest so far caused by VDPV. The first outbreak caused by VDPV was in the Dominican Republic/Haiti in 2001. But the Nigeria outbreak is of interest because it is a continuation of problems begun when the government decided to stop immunization in 2003. Although immunization has since been resumed, coverage has been low. This fact, coupled with the circulation of VDPVs in the region, led to selection of strains of VDPV that could transmit polio among hosts.

The NY Times reported on the Nigeria outbreak on 11 October 2007. Unfortunately the author of the article, Donald McNeil Jr., made two errors in the article. Here is the egregious text:

“But in rare cases it (poliovaccine) can mutate into something resembling wild poliovirus…such mutations are presumably extremely unusual”.

I wrote a letter to the Times Editor to correct these errors, but my words fell upon deaf ears. For the public record, here are my objections:

Dear Editor:

Your article of 11 October, “Polio in Nigeria” contains two errors. The vaccine does not mutate into ‘something resembling wild polio virus’; these mutated viruses are clearly vaccine-derived, not wild poliovirus. Furthermore, such mutations are not ‘extremely unusual’; they occur in nearly every recipient of the live polio vaccine. What is true is that vaccine-associated polio is extremely rare, for which we have no explanation.

Unless the public is provided with correct scientific facts, it cannot be expected to understand the ramifications of outbreaks such as those in Nigeria.