According to the 2023 Advisory Committee on Immunization Practices (ACIP), the tick-borne encephalitis (TBE) vaccine is recommended for individuals in the United States who travel to an area where the disease is endemic and are likely to have extensive exposure to infected ticks during outdoor activities. The vaccine is also recommended for laboratory workers who may be exposed to the virus. These recommendations were published in Morbidity and Mortality Weekly Report.
Members of the ACIP convened from September 2020 to March 2022 to prepare evidence-based TBE vaccine recommendations based on the epidemiology and outcomes of TBE, disease risk/burden, TBE vaccine safety, immunogenicity, and effectiveness. They used the Grading of Recommendations Assessment, Development, and Evaluation approach to analyze available data.
The Food and Drug Administration approved the TBE vaccine in August 2021 for US individuals aged 1 year and older.
Of note, a measure of protection against clinical disease conferred by TBE vaccination alone in its current formulation has not been established in the US due to a lack of data from randomized controlled trials. However, studies designed to assess vaccine effectiveness (VE) have been conducted in Europe.
Data captured from these studies on the VE of the TBE vaccine against disease and hospitalization caused by the European subtype virus indicated an estimated VE of between 91% and 99% following receipt of 3 or more doses.
Among adults (n=416) who were seronegative at baseline and received a 3-dose primary series of the TBE vaccine, 99% were seropositive between days 21 and 28 after receipt of the last dose (geometric mean titers [GMTs], 259; 95% CI, 235-285). The rate of seropositivity remained high until year 3 after completion of the series, but GMTs declined to 62 (95% CI, 53-71) at year 2 and 49 (95% CI, 42-56) at year 3.
Similar results were observed among children who received a 3-dose primary series, with seropositivity rates at or above 99% observed in all age groups. However, GMTs were lower among children aged 7 to 15 years compared with those in younger age groups.
In regard to immunologic response to a TBE booster dose administered 3 years after completion of a 3-dose primary series, a 9-fold GMT increase was observed in adults and a 6-fold increase was observed in children.
In a safety analysis, the most common local reactions following TBE vaccination were pain and tenderness at the injection site for both adults and children. Common systemic reactions included fatigue (6%) and headache (6%) in adults, and headache (11%) and fever (10%) in children.
Limitations of this analysis include the lack of data captured from special populations, including pregnant individuals and older adults.
According to the researchers, “Further research is warranted to assess the clinical spectrum of TBE virus infection during pregnancy to better understand the extent of risk for this population.”
Source: Infectious Disease Advisor
