In June 1941, after the Nazi attack on the Soviet Union, Lwów was taken over by the Germans. Weigl's institute, now renamed "Institut für Fleckfieber und Virusforschung des OKH", was kept open because, much like the Soviets before them, the Germans were interested in the applications of the typhus vaccine among their front line soldiers. The Institute was made directly subordinate to the German military, which, as it turned out, ended up giving its workers significant protection against the Gestapo. The Nazis converted a building of the former Queen Jadwiga Grammar School into Weigl's new laboratory and ordered that the production of the vaccine be stepped up, with the whole output being shipped to the German armed forces.