Safety of varicella vaccination strategies: An overview of reviews

Abstract

The safety of new vaccines under development as well as existing vaccines is a key priority for national and international public health agencies. A number of countries have implemented universal childhood varicella vaccination programmes over the past 30 years. However, strategies differ in terms of the number of doses, type of vaccine(s) recommended, age at vaccination and interval between doses for a twodose schedule. An overview of reviews was undertaken to assess the existing systematic review evidence of the safety of varicella vaccination strategies. The review was restricted to immunocompetent children aged 9 months to 6 years inclusive. A comprehensive search of databases, registries and grey literature was conducted up to 2 February 2022. Two reviewers independently screened, extracted data and assessed the methodological quality of included reviews. Overlap of included reviews was also assessed. A total of 17 reviews, incorporating both the monovalent varicella only and quadrivalent measles-mumps-rubella-varicella (MMRV) vaccines were included in the overview; six assessed the safety of one-dose strategies, four assessed the safety of two-dose strategies and 14 reviews did not specify the dosing strategy. The evidence suggests that mild local and systemic reactions are relatively common with varicella vaccination. Febrile seizures are also possible adverse effects of both the monovalent and quadrivalent MMRV vaccine, but serious adverse reactions are rare. While most reviews contained methodological flaws, and analysis by vaccine type and dosing strategy was restricted due to lack of detail in reporting of the reviews, there was clear and consistent evidence from a substantial evidence base, comprising 34 randomised controlled trials and 62 other primary studies/reviews, that varicella vaccination is safe.

Do vaccines cause epilepsy? Review of cases in the National Vaccine Injury Compensation Program

“…Likewise, Hansen et al., 46 in a study of 14 042 children receiving DTaP‐IPV/Hib vaccines, found no increase in seizures or epilepsy. In addition to DTaP/IPV/Hib, there is no indication that the meningococcal, 47 MMR, 48,49 varicella, 49,50 influenza, 51 pneumococcal vaccine, 52 hepatitis A, 53 hepatitis B, 54 and HPV 55 vaccines cause epilepsy.…”

Clinical efficacy and effectiveness of alternative varicella vaccination strategies: An overview of reviews

“…A single search was conducted to retrieve systematic reviews on the efficacy, effectiveness and safety of alternative varicella vaccination strategies, with the latter outcome reported in a separate paper. 14 A comprehensive electronic search was performed in Embase (Elsevier), Medline (EBSCO), the Cochrane Library and Google Scholar on 2 February 2022, with databases searched since inception. The SYSVAC and PROSPERO registries were also searched to identify relevant reviews and registered protocols for forthcoming systematic reviews.…”