Hepatitis B vaccination and the putative risk of central demyelinating diseases - A systematic review and meta-analysis

BACKGROUND: The anti-hepatitis B immunization campaigns launched in the early 1990s were a major public health breakthrough and targeted various populations (at-risk adults, newborns, adolescents). However, debate is still active about a possible link between this vaccine and central demyelination. This study provides a pooled estimate of this risk based on a comprehensive review and meta-analysis of all available epidemiologic studies. METHODS: A systematic review was conducted in Medline, Embase, ISI Web of Science and the Cochrane Library from database inception to 10 May 2017. Grey literature was searched and snowballing was also undertaken. Only observational studies including a control group were retained. Primary outcome was multiple sclerosis diagnosed by recognized criteria. Study selection was performed by two independent reviewers with disagreements solved through discussion. This meta-analysis based on crude, adjusted estimates, or risks limited to the 3 months following immunization was performed using a generic inverse variance random-effect model. Heterogeneity was investigated; sensitivity and subgroup analyses were performed when necessary. This study followed the PRISMA statement and the MOOSE reporting guideline (Study protocol registered in PROSPERO: CRD42015020808). FINDINGS: Of the 2804 references reviewed, 13 studies with a control group were analysed. None of the pooled risk estimates for either multiple sclerosis or central demyelination following HB immunization reached statistical significance. When considering adjusted risk ratios, the following non-significant figures were obtained: 1.19 (95%CI: 0.93 - 1.52) and 1.25 (95%CI: 0.97 - 1.62), for multiple sclerosis and central demyelination, respectively. CONCLUSIONS: No evidence of an association between hepatitis B vaccination and central demyelination was found.