Evaluation of the decision-making process underlying the initial off-label use of vaccines: A scoping review

Background: This scoping review aimed to assess the non-standardized decision-making process of National or International Immunization Technical Advisory Groups (NITAG) in developing novel off-label recommendations by examining the supportive evidence. Methods: We used the Joanna Briggs Institute framework. A search strategy was developed with a librarian to identify recommendations and evidence from peer-reviewed and gray literature until January 2022, using PubMed, Medline, EMBASE, clinicaltrials.gov, the International Clinical trials registry, governmental agency and pharmaceutical websites, the Global NITAG Network center website, and Google Scholar. Recommendations involving one of 26 pre-identified vaccine-preventable diseases, human use, and the introduction of a novel change across time and countries, were included. Evidence regarding efficacy/effectiveness, safety, or immunogenicity were included. Recommendations for fast-track approval, unlabeled or individual level off-label use, passive immunization, booster doses or provincial strategies were excluded. Only English and French documents were included. Two reviewers reviewed title/abstracts and fulltext documents, and three performed data extraction. The primary outcome was the presence and elements of the evidence. Findings: Out of 4023 documents, 12 were included, and 116 were found through manual search. Over the 40-year span captured (1982-2018), most recommendations were from the last two decades and included evidence, except three from the 1990s. Most included safety (69.2%) and immunogenicity (65.4%) studies and randomized controlled trials (57.7%). Indication-based recommendations included RCTs more often (84.6%) than posology-based recommendations (30.8%). There was evidence involving populations or vaccines different from those in the recommendation. Interpretation: Critical outcomes evidence is not systematically included in off-label recommendations, nor must it involve the exact population or vaccine(s) of concern. However, in recent years, more off-label recommendations include critical outcome evidence, mainly RCTs.