Kammala jumla mai zuwa: Bayan ƙarshen yaƙin Hirszfeld da matarsa sun koma Warsaw, inda ya kafa cibiyar serum da aka tsara bayan Cibiyar Ehrlich don Gwajin Gwajin a Frankfurt. Ba da daɗewa ba ya zama mataimakin darektan kuma shugaban kimiyya na Cibiyar Kula da Lafiyar Jama'a a Warsaw kuma, a 1924, farfesa a can. A cikin 1931 an nada shi babban farfesa a Jami'ar Warsaw kuma ya yi aiki a cikin kwamitocin duniya da yawa. Bayan da
Bayan mamayewar Poland da sojojin Jamus suka yi, an kori Hirszfeld a matsayin "ba-Aryan" daga Cibiyar Kula da Lafiya ba, amma, ta hanyar kariya daga abokai, ya sami damar yin ƙarin aikin kimiyya a gida har zuwa Fabrairu 1941; duk da haka, kusan ba zai yiwu a buga shi ba.