Tuhia he tomokanga mō tēnei wāhanga - I muri i te mutunga o te pakanga, ka hoki a Hirszfeld me tana wahine ki Warsaw, i reira i whakatū ai ia i tētahi whare rongoā i runga i te tauira o te Ehrlich Institute for Experimental Therapy i Frankfurt. Kaore i roa ka noho ia hei kaiwhakahaere tuarua me te upoko pūtaiao o te State Hygiene Institute i Warsaw, a, i te tau 1924, he kaiwhakaako i reira. I te tau 1931 i whakaingoatia ia hei kaiwhakaako tuuturu i te Whare Wananga o Warsaw a he maha nga poari o te ao. I muri i te whakaekenga o Poland
Na te ope Tiamana i peia a Hirszfeld hei "kore-Aryan" mai i te Whare Hauora, engari, na te tiaki o nga hoa, i kaha ki te mahi i nga mahi putaiao i te kaainga tae noa ki te Hui-tanguru o te tau 1941; heoi, he mea uaua ki a ia te whakaputa.