Table 1 Online vaccination information quality indices

• Functioning of links (first 3)^a

• Bar menu^a

• Ease of Use (navigability) ^ab

• Search toolbar

• Images

• Videos

• Graphs/tables/diagrams^a

• Interactivity presence and requirements^a

• Interactivity type

a) E-mail/newsletter

b) Chat rooms

c) Forum

d) Post comments

e) Other interactive services or tools (e.g., share on FB)

• Presence of title

• Medical ownership

• Target audience^a

• Date of creation

• Date of last update

• References of original contents^a

• Contacts and feedback mechanism^a

• Accreditations^a

• Advertising presence^a

• Complementarity statement

• Readability (Flesch-Kincaid Grade Level)^a

• Language/s

• Privacy Policy

• Disease information

• Treatment information

• Benefits and risks of vaccination

a) Benefits of vaccination

b) Low risks of vaccination

c) Severe risks of vaccination

• Definition of terms or (Q&A)

• Links to other vaccination related websites

a) Links to pro-vaccination websites

b) Links to Anti-vaccination websites

c) Links to other online health information resources