Abstract
Certain immunizations including vaccination against tick-borne encephalitis virus (TBEV) have been suggested to confer cross-protection against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Within a prospective healthcare worker (HCW) cohort, we assessed the potentially protective role of anti-TBEV antibodies against SARS-CoV-2 infection. Among 3352 HCW, those with ≥ 1 previous TBEV vaccination (n = 2018, 60%) showed a reduced risk of SARS-CoV-2 seroconversion (adjusted odds ratio: 0.8, 95% CI: 0.7–1.0, P = 0.02). However, laboratory testing of a subgroup of 26 baseline and follow-up samples did not demonstrate any neutralizing effect of anti-TBEV antibodies against SARS-CoV-2 in live-virus neutralization assay. However, we observed significantly higher anti-TBEV antibody titers in follow-up samples of participants with previous TBEV vaccination compared to baseline, both TBEV neutralizing (p = 0.001) and total IgG (P < 0.0001), irrespective of SARS-CoV-2 serostatus. Based on these data, we conclude that the observed association of previous TBEV vaccination and reduced risk of SARS-CoV-2 infection is likely due to residual confounding factors. The increase in TBEV follow-up antibody titers can be explained by natural TBEV exposure or potential non-specific immune activation upon exposure to various pathogens, including SARS-CoV-2. We believe that these findings, although negative, contribute to the current knowledge on potential cross-immunity against SARS-CoV-2 from previous immunizations.
Highlights
The burden of the coronavirus disease 2019 (COVID-19) pandemic shows substantial geographic variation[1]
Previous tick-borne encephalitis virus (TBEV) vaccination was associated with decreased risk of SARS-CoV-2 seroconversion with an odds ratio (OR) of 0.8 and a 95% confidence interval (CI) of 0.7–0.9 (P = 0.009)
We found an association between previous TBEV vaccination and decreased rates of SARSCoV-2 seroconversion within a prospective cohort of Swiss healthcare worker (HCW)
Summary
The burden of the coronavirus disease 2019 (COVID-19) pandemic shows substantial geographic variation[1]. Other members of the flaviviridae family include Japanese encephalitis virus (JEV) and tick-borne encephalitis virus (TBEV) and it has been hypothesized that differential burden of COVID-19 could—at least partly—be attributable to different national vaccination strategies for JEV (in Asian countries) and TBEV (in European countries)[11]. Combined, these findings prompted us to investigate any potential cross-immunity against SARS-CoV-2 mediated by anti-TBEV antibodies. We analysed baseline and follow-up samples from HCW to evaluate whether anti-TBEV antibodies showed any cross-neutralizing effect against SARS-CoV-2 and whether SARS-CoV-2 infection could increase titers of preexisting anti-TBEV antibodies
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