Bojkiewicz et al.
The prevalence of asymptomatic infections with tick-borne encephalitis virus and attitude towards tick-borne encephalitis virus vaccine in the endemic area of northeastern Poland
Vaccines. 2022;10(8):1294, doi:10.3390/vaccines10081294

In northeastern Poland, 200 to 300 TBE cases are reported yearly, of which about half of the cases occur in the Podlaskie voivodeship with local incidences reaching 4 to 10 cases per 100,000 inhabitants. Nevertheless, TBE vaccination rate is low in Poland, about 1% of the total population.

Recently, a Polish team has assessed the rate of asymptomatic TBE virus infections in northeastern Poland by measuring IgG TBE antibodies in adults (298 healthy blood donors) and 180 children (2–17 years of age, hospitalized due to viral gastroenteritis) who did not have TBE.

Of 256 adult individuals reporting neither vaccination nor being diagnosed with TBE in the past, 14 (5%) tested positive. In the pediatric group, none of them had been vaccinated nor diagnosed with TBE in the past, while a total of four children (2%) tested positive. As TBE virus is the only flavivirus circulating in Poland, it is highly unlikely that the antibodies have been induced by other flaviviruses cross-reacting with TBE virus antigens.

The authors concluded that the seropositivity in TBE antibody-positive persons have been caused by asymptomatic or very mild afebrile infections, and the rate of mild or asymptomatic infections seems to be high in northeastern Poland showing an urgent need to raise awareness and knowledge about the benefits and importance of TBE vaccination.

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