Vlasic cleared 6 feet, 4¼ inches on Saturday on a cold, rainy afternoon in New York that made her foot ache.
Olympic silver medalist Michael Tinsley used the weather to his advantage to win the 400 hurdles, staying relaxed then coming from behind at the end when the wind was at his back.
Two-time Olympic champion Veronica Campbell-Brown of Jamaica took first in the 200, while reigning world champ Amantle Montsho won the 400.
Olympic gold medalist Sanya Richards-Ross, recovering from toe surgery, pulled out after deciding her foot wasn't ready to return to competition.