Background Social media allow users to quickly spread information and opinions. Unfortunately, it is often a place of anti-vaxxers activity, who create content that spreads easily. This situation leads to an increase in vaccine hesitancy and may result in outbreaks of infectious diseases. We wanted to find and characterize what negative arguments against the COVID-19 vaccines Facebook users create and how the popularity of the allegations against vaccines changes over time. Methods We followed the posts published on Facebook by the biggest Polish media. We have selected the highest commented events related to the registration and introduction of the COVID-19 vaccines. Then, we analyzed user comments related to those events and established the main themes of anti-vaccine comments. Using this list of topics, we categorized 3414 comments and checked the frequency of comments from given categories and their variability over time. Results The arguments of vaccine opponents about the COVID-19 vaccines can be divided into 12 categories. Seven of them also apply to other vaccines but five types are COVID-19' specific. Two new arguments say that vaccines were not properly tested or do not exist. The third topic mentions the history of the swine flu vaccine and the following narcolepsy cases. The fourth category suggests that vaccine against COVID-19 existed before the pandemic. The last argument says that no one takes responsibility for the side effects of the vaccine. The frequency of arguments from a given category varies over time. We also noticed that, while the comments were mostly negative, the reactions were positive. Conclusions Our codebook of anti-vaccine topics can help public health professionals better understand social media content. Real-time monitoring of social media is important because the popularity of certain arguments on Facebook changes rapidly over time but early recognition of social doubts allows for targeted interventions. Key messages Online anti-vaccine comments on the COVID-19 vaccines can be divided into 12 topic categories. The frequency of Facebook comments against COVID-19 vaccines from a given topic category varies over time.
The Arguments of the COVID-19 Vaccines Opponents on Facebook in Poland: Textual Analysis Study