Table 5.

Synthetic summary of the main findings of each category of studies included in this systematic review, in addition to their implications for public health policy.

Characteristic of studies	Summary of main findings	Implications for public health policy
(1) Cross-sectional studies reporting the association between reliance on social media and vaccine hesitancy and/or acceptance	Overall, reliance on social media was associated with increased hesitancy. Further research is warranted to explore the role age plays in this association, given that two studies conducted among young adult populations reporting an opposing association.	Understanding social media usage patterns can provide an opportunity for targeted intervention. Studies of this characteristic provide evidence that users derive their information from social media. Hence, targeting appropriate public health communication and battling misinformation has the potential to shape people's attitudes regarding public health efforts.
(2) Studies that performed thematic-analyses of extracted social media data, thereby reporting discussions related to COVID-19 vaccine intentions/opinions	Overall, anti-vaccination discussions were more prevalent on various social media platforms. Additionally, echo chambers phenomena were observed relating to anti-vaccination campaigns. Discussions on social media provided valuable insights regarding reasons regarding vaccine hesitancy or acceptance. Finally, there is a potential role for social media influencers, especially doctors, to increase vaccine acceptance among the public.	Studies in this category demonstrated the potential for polarized views to be amplified using social media. Understanding this notion has profound benefits for targeting misinformation and combating false-news preaching “bubbles” that can be formed on social media. When designing intervention measures, it may be more beneficial to target specific anti-vaccine campaigns and misinformation rather than solely increasing the number of vaccine-encouraging content on social media
(3) Studies that explored the degree of polarization of specific social media contents related to COVID-19 vaccines (the degree of positive vs negative sentiments);	In general, studies reported a similar degree of positive and negative toning in terms of social media content relating to vaccination.	Social media provides an opportunity to evaluate and understand public sentiment about vaccinations in real-time, in a quick and efficient manner. Utilizing social media to understand public's sentiment allows for tailored and targeted intervention, specific to the current views held by the public.
(4) Studies that explored the fluctuations of vaccination attitudes/opinions gathered from social media depending on specific events that were identified as trigger events.	People's sentiment regarding COVID-19 vaccination varies greatly with specific key events relating to vaccination, both positively and negatively.	A thorough understanding of how specific events trigger people's emotions can be crucial for governments and public health officials to identify appropriate times of intervention to maximize benefit and guarantee the population's cooperation and engagement. Findings from those studies demonstrate that it is crucial for the government to adjust vaccination policies promptly in response to the public health events to promote massive vaccination via dynamic monitoring public sentiments.