Vaziri, who is swimming at her first world championships,
clocked a time of 28.16 seconds, 0.03 of a second quicker than the existing
record set by Germany's Janine Pietsch in 2005.
Pietsch swam in Vaziri's
semi final but could only manage third place in a time of 28.72, behind the
American and Japan's Mai Nakamura (28.59).
The semi belonged to Vaziri
who swam a fantastic sprint. She launched herself off the wall with plenty of
power and maintained her dominating lead ahead of Nakamura for the race's
The 20-year-old broke the championship record on Wednesday
morning in the heats and bettered her personal best time yet again in the semi
finals. Everyone will be waiting to see if she can back it up again in Thursday
"It's the first time I've swum the 50m backstroke so it
was unexpected, but I was ready. I missed the top eight in the 100m backstroke
so I was ready to go in the 50m," she said.
Aliksandra Herasimenia of
Belarus qualified second fastest for the final after winning the first semi in a
time of 28.38.
The three swimmers in the middle lanes of that race -
Herasimenia, Reiko Nakamura and Jing Zhao - were equal across the pool for much
of the time but it was the Belarusian who took the lead.
qualified third fastest (28.58), Mai Nakamura (28.59) fourth and Pietsch took
fifth place. China's Zhao Jing was sixth (28.74) and Australian Tayliah Zimmer
seventh (28.78). Another Chinese Gao Chang will take the final place in
Thursday's final (28.81).