The Croatian returned to competition this year after missing the whole of 2012 following surgery on her Achilles tendon.
"The pain in my foot became more intense after the Diamond League competition in Monaco (on July 19) and it still has not calmed down as after the other competitions," she wrote on her website.
"This is a clear sign that I need to stop for a while and recover completely. To jump in Moscow would be too much of a risk and could only jeopardize the future and I don't want to risk that."
Vlasic became world champion for the first time in Osaka in 2007 and retained her title in Berlin two years later. She was a silver medallist behind Russian Anna Chicherova two years ago in Daegu, South Korea.
Vlasic, 29, had a best leap of 2.0 metres this year, a height bettered only by Chicherova and American Brigetta Barrett.
The world championships run from August 10-18.
- Sports & Recreation