Cervarix is a recombinant human papillomavirus (HPV)-16 and -18 L1 virus-like-particle (VLP) AS04-adjuvanted vaccine designed to protect against cervical intraepithelial neoplasia and cervical cancer caused by the HPV types 16 and 18. Assessment of the stability of the vaccine during long-term storage and after transient exposure to temperatures out of normal storage range is an integrated part of vaccine quality evaluation. This assessment was done with vaccine samples stored at 2-8 degrees C for up to 36 months, with or without simulated cold chain break (either one week at 37 degrees C, or two or four weeks at 25 degrees C). Among the stability-indicating parameters, antigenicity and immunogenicity were evaluated along with L1 antigen integrity and adsorption to aluminum. Differential scanning calorimetry (DSC) was used to investigate the structural stability of the VLPs before and after vaccine formulation and over time. Cervarix was stable at 2-8 degrees C for at least three years, and the occurrence of cold chain break had no impact, as shown by unchanged product characteristics during the full storage period. DSC analysis demonstrated that the structure of the HPV-16 and -18 L1 proteins and their corresponding VLPs was not affected throughout the manufacturing process. Moreover, the structure of aluminum-adsorbed HPV-16 and -18 L1 VLPs was robust over a 14-month test period. In conclusion, Cervarix was very stable upon long-term storage at 2-8 degrees C with or without transient exposure to higher temperatures (up to 37 degrees C). The observed robust structure of the L1 VLPs contributes to the excellent stability of Cervarix.