A vial adapter assembly (100, 200, 300, 400) for a closed fluid transfer system, the vial adapter assembly comprising: a vial adapter, including: a base defining an inner annular rim and an outer annular rim and a cavity therebetween; an annular stem extending from the base and defining an opening having a plurality of fingers extending around the opening thereof, wherein each finger defines a proximal recess and a distal recess formed therein; a cover supported on the outer annular rim, wherein an expansion chamber is defined within the cover and the base; an adapter support situated within the cavity of the base, the adapter support including: a male stem extending in a first direction from the base, the male stem selectively connectable to and insertable into an open distal end of a syringe adapter, the male stem defining a lumen extending therethrough; a seal extending across the lumen of the male stem; and a spike extending in a second direction from the inner annular rim and into the opening of the annular stem, wherein the spike includes a first lumen being in fluid communication with the lumen of the male stem, and wherein the spike includes a second lumen being in fluid communication with the expansion chamber; and a bladder extending between the base and the cover; and a vial collar including: an annular body configured and dimensioned for sliding receipt within the annular stem of the vial adapter; at least one tab projecting from an outer surface of the annular body and being configured for selective receipt in distal recess and proximal recess of a respective finger of vial adapter; and at least one retainer projecting from an inner surface of the annular body. a vial adapter, including: a base defining an inner annular rim and an outer annular rim and a cavity therebetween; an annular stem extending from the base and defining an opening having a plurality of fingers extending around the opening thereof, wherein each finger defines a proximal recess and a distal recess formed therein; a cover supported on the outer annular rim, wherein an expansion chamber is defined within the cover and the base; an adapter support situated within the cavity of the base, the adapter support including: a base defining an inner annular rim and an outer annular rim and a cavity therebetween; an annular stem extending from the base and defining an opening having a plurality of fingers extending around the opening thereof, wherein each finger defines a proximal recess and a distal recess formed therein; a cover supported on the outer annular rim, wherein an expansion chamber is defined within the cover and the base; an adapter support situated within the cavity of the base, the adapter support including: a male stem extending in a first direction from the base, the male stem selectively connectable to and insertable into an open distal end of a syringe adapter, the male stem defining a lumen extending therethrough; a seal extending across the lumen of the male stem; and a spike extending in a second direction from the inner annular rim and into the opening of the annular stem, wherein the spike includes a first lumen being in fluid communication with the lumen of the male stem, and wherein the spike includes a second lumen being in fluid communication with the expansion chamber; and a bladder extending between the base and the cover; and a vial collar including: an annular body configured and dimensioned for sliding receipt within the annular stem of the vial adapter; at least one tab projecting from an outer surface of the annular body and being configured for selective receipt in distal recess and proximal recess of a respective finger of vial adapter; and at least one retainer projecting from an inner surface of the annular body. an annular body configured and dimensioned for sliding receipt within the annular stem of the vial adapter; at least one tab projecting from an outer surface of the annular body and being configured for selective receipt in distal recess and proximal recess of a respective finger of vial adapter; and at least one retainer projecting from an inner surface of the annular body.