*Tweets* We retrieved all Dutch Twitter messages (statuses or tweets) written between 07-28-17 and 12-02-17 that included the words: ‘vaccinatie’, ‘vaccineer’, ‘vaccineert’, ‘vaccineren’, ‘vaccineerde’, ‘vaccineerden’, ‘gevaccineerd’, ‘gevaccineerden’, ‘vaccin’, ‘vaccins’, ‘inenting’, or ‘inenten’ . This produced a collection of 2,869 tweets by 1,684 unique users. Many of these tweets resulted from (multiple) interactions between users. For example, 823 of our 2,869 original tweets (28.7%) were replies, 414 (14.4%) were retweets, and 249 (8.7%) were quotes. Many of these statuses would not have been written without an original tweet to retweet, quote, or reply to. As we wanted our data to reflect this context, we retrieved the (chains of) tweets that triggered the retweets, quotes, and replies in our initial set, resulting in 2,437 extra tweets by 1,197 unique users, of whom 324 unique users were present in our initial data set. This led to a sample set of 5,306 unique messages written by 2,557 unique users. ...