My Health Record (MHR), which is an online health summary for Australians, was changed from the opt-in to the opt-out model, and therefore sparked a vast discussion on Twitter. In order to understand the debate, the information dissemination and the levels of engagement, we have analysed tweets posted from July 2018 to February 2019. In this paper, we report on the findings of the patterns of discussion, the hashtags and the numbers of retweets and likes from different user categories. The results show that the discussion was highly political, and the tweets from the MHR official accounts had lower propagation and engagement than other user groups. This work highlights the implications of using social networking sites (SNSs) to promote large-scale mandatory electronic health record systems.