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This study compared COVID-19 vaccine-related material from two popular social media platforms, Reddit and Twitter from January 1, 2020, to March 1, 2022. These two platforms were chosen due to their worldwide usage, vibrant discussions, and high user count. The timeframe included the earliest parts of the pandemic to trace the evolution of sentiments over time. Most importantly, these platforms were chosen because only a small number of comparative studies focused on the typical user, especially related to COVID-19 vaccine sentiment or other vaccine content. 
Significant effort was taken to identify and remove Twitter postings that were found to be directly from news agencies or bots. These posts were identified due to an overwhelmingly high post count during the 26-months period relative to the average posting of a “normal” user as well as by visually inspecting tweets of users that appeared at an abnormal frequency. Both Twitter and Reddit datasets were limited to only include users who posted less than or equal to 200 times throughout our timeframe. These steps were important due to the repetitive nature of many bot tweets which had the potential to skew sentiment calculations and misalign the goal to compare the normal user base of both platforms. Though methodologies in harvesting Reddit and Twitter data differ slightly, both datasets underwent similar cleaning steps. Both were queried for the same relevant terms typically present in online discussions about COVID-19 vaccines. This step was important due to the tendency for some extended comment threads to meander off-topic. This occurrence was especially true with threads from some Reddit communities. The posting frequency of the two platforms was relatively similar in the early months of the pandemic. Frequency increased dramatically for both platforms in late September 2020-October 2020 as news of the vaccine roll became more widespread. Though each platform displays four spikes in posting frequency a similar times (Oct 2020, Mar-Apr 2021, Aug-Sep 2021, Dec 2021-Jan 2022) they each obtain a maximum in different months. Reddit reached its maximum posting in Mar-April 2021 while Twitter reached its maximum in Sep-Oct 2021. 
Twitter Data
Approximately 13 million Tweets were harvested using the snscrape (document) and Tweepy API Python libraries (document). After removing tweets by suspected bots,  news media, highly repetitive-high frequency users, or duplicate Tweets, our final Twitter data set consisted of 9,518,270 Tweets authored by 3,006,075 Twitter users. The Tweets contained a total of approximately 16.32 million likes with a maximum of 430,758 and an average of 14.9. Tweets cannot be downvoted but approximately 4,794,865 had zero likes attributed. Statistics on tweet sharing or retweets were not collected because this metric was not available for both platforms.

I also collected vaccine-related data from the Reddit information-sharing social media platform that is currently accessed by approximately 430 million users with approximately fifty percent located in the U.S. The platform is composed of user-created communities (subreddits), in which members adhere to a set of community regulations. Subreddit members have the option to post links, images, videos, and text. Community members then typically "upvote" or "downvote" on a post based on their opinion of the quality of that post and/or leave comments. Depending on the distribution of votes, posts are classified as hot, new, rising, and controversial. The most popular posts within each category are then moved to the top of the community page. These comments are subjected to the same vote ranking system. The upvote/downvote system within Reddit is intended to increase the quality of the posts to minimize non-relevant material. 

Reddit data were gathered in three phases of this study and therefore there are three Reddit (R1, R1.2,  and R2). For the R1 data set, I harvested approximately 18,000 posts from thirteen subreddits through the Reddit API on May 16, 2021. Because Reddit communities potentially contain some inherent bias due to strict community rules, as well as content monitoring by a moderator, these subreddits were chosen to create a non-biased dataset from a diverse selection of communities that vary widely in political views as well as position on vaccination. These subreddits were also chosen due to a large number of members (approximately five million members). Data were cleaned first by combining each subreddit into a centralized database. The data were then organized by date and then queried for terms specifically related to the COVID-19 vaccine. These terms included COVID vaccine, vaccine, vaccination, immune, immunity, COVID vaccination, corona vaccine, COVID19 vaccination, COVID-19 vaccination, coronavirus vaccination, coronavirus vaccine, COVID-19 vaccine, coronavirus vaccine, coronavirus vaccination, Moderna, Pfizer, J&J, Johnson & Johnson, COVID vax, corona vax, covid-19 vax, covid19 vax, coronavirus vax). Our finalized dataset consisted of 1401 posts and 10,240 comments (11,641 in total) written by greater than or equal to 8281 authors/users, 1048 of whom posted multiple times. In actuality, the number of authors could have been as high as 9013. These additional users are probable because Reddit removes the user ID from posts after a user deletes their account. However, the post content and upvotes remain.