doubt about combobox

I have 2 combobox, one to list country an when my user select a list I list the cities in another combobox, but my users are typing so fast and go to the tab to change the combo box to select the city. But as when the user starts typing the country vaadin goes to the server to retrieve the list in the meantime the user has already pressed the tab and left the component thus losing the whole process, and it is possible that I already leave the list of parents in the front ? so you do not have this delay when typing?