Advances in sperm vitrification and clinical translation from conventional semen to precision preservation of rare spermatozoa

Sperm vitrification is an important area of research in male fertility preservation and assisted reproduction. This narrative review distinguishes operationally defined vitrification from related freezing methods and includes a targeted literature update through 3 October 2026. Its effectiveness depends on more than an exceptionally high cooling rate. Microvolume loading, efficient heat transfer, and appropriate cryoprotection must work together to suppress ice formation while minimizing osmotic stress, oxidative damage, and warming-associated injury. Laboratory evidence suggests that some vitrification protocols improve post-warming sperm motility, whereas benefits for DNA integrity remain inconsistent. Outcomes depend on baseline sample quality, sperm source, cryoprotective formulation, carrier design, and cooling and warming conditions. Research has increasingly moved beyond comparisons with slow freezing toward optimization of cooling and warming kinetics, functional additives, microfluidics, and precision preservation of small numbers of spermatozoa or individual cells. Vitrification cannot yet replace established conventional freezing methods across clinical settings. Its greatest potential may lie in severe oligozoospermia, cryptozoospermia, surgically retrieved sperm, and the preservation of individual or very few spermatozoa. Further progress requires standardized, reproducible protocols, traceable recovery, and appropriate quality assurance and biosafety measures. Evaluation must also extend beyond post-warming laboratory measures to fertilization, embryo development, clinical pregnancy, live birth, and long-term offspring health. A continuous evidence base linking technical performance to clinical benefit is needed to define the role of sperm vitrification in male fertility preservation and assisted reproduction.