FREETOWN, Sierra Leone – The health ministry says a polio vaccination campaign in the West African nation of Sierra Leone is being delayed because of European flight problems caused by volcanic ash.

The polio campaign was to begin Friday but the vaccines were to come from Copenhagen.

The weeklong airspace closures in Europe caused by the ash threat to planes represented the worst breakdown in civil aviation on the continent since World War II.

The ash cloud has had drastic consequences in parts of Africa — showing how one event can have a big impact in today's global economy.

In Kenya, thousands of day laborers are out of work because produce and flowers can't be exported amid the flight cancellations. And in Ghana, the flight delays have hurt pineapple growers who export to Europe.