Zimbabwe starts an emergency polio vaccination drive after detecting cases caused by a rare mutation

Zimbabwe has started an emergency campaign to inoculate more than 4 million children against polio after health authorities detected three cases caused by a rare mutation of the weakened virus used in oral vaccines

HARARE, Zimbabwe -- Zimbabwe began an emergency campaign to inoculate more than 4 million children against polio on Tuesday after health authorities detected three cases caused by the rare mutation of the weakened virus used in oral vaccines, including a 10-year-old girl who was paralyzed in January.

The health ministry said laboratory tests from samples collected from sewage sites in several areas of the capital, Harare, late last year showed the presence of a mutated polio virus that originated in an oral vaccine used in the global eradication effort.

In rare instances, the live polio virus in vaccines can mutate into a form capable of sparking new outbreaks, especially in places with poor sanitation and low vaccination levels.

The number of polio cases globally has dropped by more than 99% since the global effort to wipe out the disease led by the World Health Organization and others began in 1988. But the majority of children being paralyzed by polio these days are being crippled by a virus that was originally linked to a vaccine.

Vaccination teams in Zimbabwe are moving from house to house to deliver more doses to protect children, while others will be stationed at health facilities, authorities said.