Resources for assessing parents’ vaccine hesitancy: a systematic review of the literature

Vaccine hesitancy (VH) is a complex and country-specific issue, responsible for the decreasing vaccination rate and subsequent spread of vaccine-preventable diseases. In literature, several questionnaires were developed to assess VH. The aim of this systematic review was to evaluate the published questionnaires assessing parental VH. The search was conducted in PubMed/Medline, Web of Science and The Cochrane Library, in December 2017, following the PRISMA guidelines. The search strategy included 4 types of keywords: parents, vaccine hesitancy/acceptance, immunization and survey. Only English and Italian original papers were included. 17 reviewers independently screened titles and abstracts. Only the included articles were downloaded in full and, after a second screening, data were extracted and recorded in an ad hoc spreadsheet. A total of 5,139 articles were retrieved, after duplicates elimination 3,508 papers were screened. After a screening selection, 334 studies were included in the analysis. Most studies were cross-sectional (92.8%), followed by case-control (4.8%) and cohort studies (2.4%). The population interviewed was mainly parents, without any further details (73.1%); mothers were the only parent surveyed in approximately 20% of the studies, while only 1 study involved selectively the fathers. The sample size ranged from 7 to 59,897. Only 38% of the included studies reported both the number and type of items used. Regarding the type, more than half consisted of closed questions, followed by Likert scales, while open-ended questions were used in 14.8% of the surveys. Frequently, the survey was conducted using a self-reported questionnaire or interview. The questionnaires were mostly administered on paper, while online forms were used in 20.1% of the cases. However, 80.2% of the questionnaires were not attached to the paper. HPV vaccine was the most frequently investigated (39.2%), followed by influenza (13.5%) and measles (10.8%). While 22.4% of the articl