Decreasing humoral response among healthcare workers up to 4 months after two doses of BNT162b2 vaccine. Issue 2 (February 2022) - Ferré, Valentine Marie; Lebourgeois, Samuel; Menidjel, Reyene; Collin, Gilles; Chenane, Houssem Redha; Guindi, Manuella Onambele; Yazdanpanah, Yazdan; Timsit, Jean-François; Charpentier, Charlotte; Descamps, Diane; Fidouh, Nadhira; Visseaux, Benoit