**4. Measures**

To measure *belief in conspiracy theories about vaccines/vaccination*, we used a 7-point Likert scale with seven items, ranging from 1 (believe to be completely false) to 7 (believe to be completely true). Given the high proliferation of conspiracy theories about vaccines and vaccination within the current media environment [93], we asked respondents to judge seven statements related to prominent narratives that were spread in the media during the COVID-19 pandemic claiming that the vaccination of children is dangerous and is kept secret, that the link between vaccines and autism is kept secret, that people are being fooled about the effectiveness and the safety of vaccines, that data on vaccine safety and effectiveness are often fabricated, and that pharmaceutical companies hide the dangers of vaccines. The items were loaded on one factor, with loadings ranging from 0.818 to 0.892 (*α* = 0.939, *M* = 3.68, *SD* = 1.76).

*Age* was measured in years old ( *M* = 43.11, *SD* = 13.08).

To measure *education*, we used an 8-point ordinal scale from 1 (*no education at all*) to 8 (*graduate studies*) ( *M* = 5.92, *SD* = 1.28).

To measure *religiosity* (the frequency of going to church component), we asked participants about the frequency of going to church on a 7-point Likert scale ranging from 1 (*daily*) to 7 (*never or almost never*) ( *M* = 4.91, *SD* = 1.30). We used this particular type of measurement in order to better cover the behavioral component of religiosity rather than self-perceived religiosity because the frequency of going to the church might, in some cases, show a stronger commitment to religious beliefs.

To measure *critical thinking disposition* (the reflective skepticism component), we used a 7-point Likert scale with four items, ranging from 1 (*very unlikely*) to 7 (*very likely*). The scale was adapted from Sosu (2013) [94]; we asked respondents to assess whether the following statements were applicable to them: "I often re-evaluate my experiences so that I can learn from them", "I usually check the credibility of the source of information before making judgements", "I usually think about the wider implications of a decision before taking action", and "I often think about my actions to see whether I could improve them". The items were loaded on one factor, with loadings ranging from 0.830 to 0.892 (*α* = 0.882, *M* = 5.61, *SD* = 1.22).

To measure *perceived usefulness of SNS* (mainly for information-related purposes)*,* we used a 7-point Likert scale with three items, ranging from 1 (*to a very little extent*) to 7 (*to a very great extent*). The scale was adapted from Lee and Choi (2018) [95]; we asked respondents to judge the extent to which the following statements they considered correct for them: "I usually take information through SNS", "I utilize information gained from SNS", "I immediately update information received from SNS". The items were loaded on one factor, with loadings ranging from 0.903 to 0.922 (*α* = 0.895, *M* = 3.83, *SD* = 1.71).

To measure *perceived incidence of fake news about COVID-19 vaccines/vaccination*, we asked respondents to estimate the percentage of COVID-19-vaccine-related news (out of the total percent of news) they believe to be counterfeit or even false (*M* = 50.21, *SD* = 26.01).

To measure *frequency of COVID-19 news consumption from websites, SNS, and IM apps*, we used three items, rated on a scale ranging from 0 (*no consumption at all*) to 7 (*every day consumption*); the scale was used in other studies [96] and it approximated the number of days in the previous week that people consumed COVID-19-related news from websites (other than official websites and social networking sites), SNS (such as Facebook, Instagram, Twitter, etc.), and IM apps (such as WhatsApp, Facebook messenger, etc.). The items were loaded on one factor, with loadings ranging from 0.835 to 0.880 (α = 0.819, *M* = 2.49, *SD* = 2.21).
