We review 100 articles published from 2000 to early 2020 that research aspects of vaccine hesitancy in online communication spaces and identify several gaps in the literature prior to the COVID-19 pandemic. These gaps relate to five areas: disciplinary focus; specific vaccine, condition, or disease focus; stakeholders and implications; research methodology; and geographical coverage. Our findings show that we entered the global pandemic vaccination effort without a thorough understanding of how levels of confidence and hesitancy might differ across conditions and vaccines, geographical areas, and platforms, or how they might change over time. In addition, little was known about the role of platforms, platforms’ politics, and specific sociotechnical affordances in the spread of vaccine hesitancy and the associated issue of misinformation online.
[…]