Grau Cerrato, SantiagoMartín García, Elena, 1975-Ferrández, OliviaMartín, RaquelTejedor Vaquero, Sonia, 1988-Gimeno, RamónMagri, Giuliana, 1978-Maldonado, Rafael, 1961-2022-06-162022-06-162022Grau S, Martín-García E, Ferrández O, Martín R, Tejedor-Vaquero S, Gimeno R, Magri G, Maldonado R. COVID-19 mRNA vaccines preserve immunogenicity after re-freezing. Vaccines (Basel). 2022 Apr 12;10(4):594. DOI: 10.3390/vaccines100405942076-393Xhttp://hdl.handle.net/10230/53505The massive COVID-19 vaccine purchases made by high-income countries have resulted in important sample losses, mainly due to the complexity of their handling. Here, we evaluated the possibility of preserving the immunogenicity of COVID-19 mRNA vaccines after re-freezing vials, following the extraction of the maximum possible number of samples, as an alternative approach to minimizing their wastage. Thus, we exposed the vaccine vials to different re-freezing conditions and evaluated mRNA integrity and the effects in mice after in vivo administration. We reveal that the mRNA integrity of Comirnaty® and Spikevax® vaccines remained unaffected after re-freezing during 1 month at -20 °C or -80 °C. The immunological responses also remained unchanged in mice after these re-freezing conditions and no apparent side effects were revealed. The preservation of mRNA integrity and immunogenicity under these handling conditions opens the possibility of re-freezing the mRNA COVID-19 vaccine vials to limit their wastage and to facilitate vaccination processes.application/pdfeng© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).info:eu-repo/semantics/articlehttp://dx.doi.org/10.3390/vaccines10040594COVID-19SARS-CoV2mRNAVaccinationVaccine preservationVaccine wastageinfo:eu-repo/semantics/openAccess