Protection against tick-borne encephalitis with a new vaccine formulation free of protein-derived stabilizers

Abstract

Background: Vaccination against tick-borne encephalitis (TBE) has been successfully employed for many years in TBE-endemic countries. Post-marketing experience gained from widespread use, however, prompted the development of improved TBE vaccines, the most modern versions of which do not contain the commonly used protein-derived stabilizers (human albumin or polygeline) of former vaccines. Method: This article summarizes both the medical need for and clinical experience with a new TBE vaccine formulation (pediatric and adult versions). To this end, data from clinical trials and post-marketing experience are presented. The clinical database comprises immunogenicity and/or safety data of approximately 7,500 subjects ages 1 to 77 years who participated in eight clinical trials. The clinical trials were conducted at 69 centers in five European countries. Post-marketing experience includes safety data from passive pharmacovigilance systems in 18 countries where these vaccines have been licensed since 2001. Results: All subjects analyzed for immunogenicity achieved postimmunization levels of TBE antibodies that meet the definition of seroconversion or represent a fourfold increase. The pooled data of clinical trials revealed the expected rate of solicited local and systemic reactions. The majority of these transient postimmunization reactions were mild. Pharmacovigilance data confirm the high level of safety of these new TBE vaccines: only a common range of the side effects already noted for licensed TBE vaccines was reported. After the distribution of more than five million vaccine doses, no potential safety risk was noted. Conclusion: Post-marketing experience supports results from clinical trials showing that these new TBE vaccines may safely be used for the vaccination of children, adolescents, and adults.