Following the COVID-19 outbreak– which is an alarming “public health emergency of international concern” (WHO 2021a)– public interest in vaccination grew, resulting in the rapid circulation of vaccination- related information, particularly through social media, such as Facebook and Instagram. Terminological content referring to scientific concepts (i.e. inactivated viral vaccine, vaccine prioritisation, etc.), quickly took hold at country and global levels, to describe all facets related to vaccination. However, it was not clear to what extent the WHO official terminology was being used by governments and authorities and how this was disseminated to local populations, for instance via social media.

The present study focuses on terminology in Arabic used in COVID-19 vaccination- campaign messages delivered across a group of Arabic- speaking countries, namely Qatar, Saudi Arabia, Tunisia and the United Arab Emirates (UAE). Its objective is twofold: first, to investigate the extent of overlap between international health resources produced by the World Health Organization (WHO) and official vaccination- related content developed by each of the four countries; and second, to review whether or not health- related terminology in the context of COVID-19 was marked by variations between those countries as well as by versions used on social media. After a brief review of the literature to establish the concept of communication in emergency situations, an overview of official campaigns related to COVID-19 and Arabic web- based health information is given. The general question is then set, followed by the definition of the concept of localisation that stems from the analysis of terminological contents in this study. Research questions are then presented (first section of the chapter). While analysing a corpus of terms related to the WHO and the selected countries separately, we study how the COVID-19 vaccination terminology was used in the specific country contexts in light of the WHO campaigning contents (second section). The third section then highlights the results related to COVID-19 vaccination terminology at the WHO international level, as well as the country- specific level, and the communication strategies used in the case of terminological localisation.