The OPERA survey online platform, already developed and used, and an implemented data warehouse (IT.CO.ME.S) utilised for research purposes is used for this study. Data entered is encrypted with a symmetric keys procedure and sent over the internet using an ad-hoc software named COME Survey, which is developed specifically for this purpose to run highly secure surveys and studies containing potentially sensitive data. This system transfers data (microdata census) to a certified data centre; all information is processed and hosted following data protection regulations. Answers are anonymised, and IP addresses are not disclosed to the research team. The system automatically manages the link between email address, StudyID and survey status, which means that research staff are not able to identify the responses provided and that double response is not allowed. Only OPERA research personnel have access to the complete, anonymised dataset
.