An outbreak of poliomyelitis in northern Nigeria that began in 2006 and resulted in 69 confirmed cases of paralysis was caused by a mutated strain of the live polio vaccine, according to a new report (MMWR Morb Mortal Wkly Rep. 2007;56:996-1001).
Vaccine-related polio, which occurs when live weakened poliovirus used in the vaccine strain mutates, is rare; however, low vaccination rates in a region make it possible for the virus to spread through the population. In Nigeria, the outbreak followed a nearly year-long period beginning in 2003 when immunization efforts were suspended due to rumors that the vaccine caused sterility or AIDS. In 2005, 15% to 50% of children younger than 5 years in 7 of 9 northern states had not received a single dose of the vaccine; immunization campaigns helped improve coverage, although 5% to 30% of children in the north remained unvaccinated by the end of 2006.
Stephenson J. Polio in Nigeria. JAMA. 2007;298(19):2254. doi:10.1001/jama.298.19.2254-a