The paper investigates the thematic patterns of health awareness campaigns made during the COVID-19 pandemic. The aim is to scrutinize the types of themes used in such prosocial advertisements by analyzing the theme placement and the elements inside those themes. COVID-19 was declared a global pandemic in 2020 due to which health organizations proceeded to spread warnings and health awareness campaigns. In these circumstances, the language of these campaigns played a significant role in delivering the message to the people. In total, 75 posts were taken from official Instagram accounts of the World Health Organization (WHO) and the Centre for Disease Control (CDC) between March 21st, 2020 and June 21st, 2020. In this mixed-method study, a quantitative method has been used to obtain the ratio of unmarked and marked themes present in the data, which are further analysed qualitatively with Halliday’s (1994) theme-rheme model. We found that the majority of the clauses use unmarked themes, while marked themes are not as frequent. Through the preference of simple Theme over multiple Theme, complex language structure (clause-complex) has been avoided. This shows the awareness of respective organizations regarding the critical role language plays in influencing the audience, especially during a global health crisis.