Gullo G, Petousis S, Papatheodorou A, et al. - Researchers investigated the efficacy of open vs closed vitrification protocols for sibling-oocyte cycles when performing blastocyst embryo transfers. In this prospective study in oocyte recipients sharing sibling oocytes between 2014 and 2016, random and equal assignment of sibling oocytes into the closed group (oocytes vitrified in a closed system) or the open group (oocytes vitrified in an open system) was performed. All cases received intracytoplasmic sperm injection. On day 5, embryo transfers were performed. As per power analysis calculation, each group would require 94 cycles in the study in order to achieve statistical significance at a 5% level with power 80%. Inclusion of a total number of 95 donors was done finally. This study involved a total of 190 recipients matched with their donors.  Outcomes suggest equal effectiveness of open and closed vitrification protocols for sibling-oocyte cycles.