The vacancies produced in high energy collision cascades can form in irradiated tungsten vacancy clusters or vacancy prismatic dislocation loops. Moreover, vacancy loop can easily transform to a planar vacancy cluster. We investigated the formation energies of these three types of vacancy defects as a function of number of vacancies using three EAM tungsten potentials. The most favorable defect type and vacancy loop stability was determined. For very small sizes the planar vacancy cluster is more favorable than a vacancy loop, which is unstable. The void is the most stable vacancy defect up to quite large size, after that vacancy dislocation loop is more favorable. We however assume that the vacancy dislocation loops are nevertheless stable at low temperatures as the transformation to voids would need high temperature.