A critical requirement for CTL epitope-based strategy is to identify and select promiscuous CTL epitopes that bind to several alleles of HLA supertypes to reach maximal population coverage. The utilization of supertyperestricted epitopes, which bind with significant affinity to multiple related HLA alleles, provides solution to this problem [117] . As described before, 80-90% population coverage can be achieved in most prominent ethnicities by focusing on only three major HLA class I supertypes -A1, -A3 and -B7 [132, 133] . By including two additional supertypes (A1, A24), 100% population coverage in all major ethnicities could be reached [117, 132] . Recently, HLA class I -A2, -A3 or -B7 supertype-restricted epitopes conserved among different viral subtypes of influenza virus were identified, what could be of relevance for the development of a potential supertype-restricted, multiepitope CTL-based vaccine protective against any subtype of influenza virus [82, 103, 113, 134] .