All flaviviruses have been found to be antigenically-related, meaning that immunological memory (‘original antigenic sin’) can occur that modulate immune responses to sequential infections and/or vaccinations. The authors were interested in the influence of pre-existing yellow fever virus (YFV) vaccine-derived immunity on the antibody response to tick-borne encephalitis virus (TBEV) vaccination. They compared samples from YFV pre-vaccinated and flavivirus-naive individuals and found that YFV immunity causes significant impairment to the neutralising antibody response to TBEV vaccination and also reduces specific TBEV neutralising activities. Therefore there may be a possible negative effect of pre-existing cross-reactive immunity on the outcome of flavivirus vaccination.
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