where ci denotes the sum of cross-immunity to strain j isolated in season τ of 1992.0 ≤ τ ≤ t; that is
The gi indicates the thermodynamic stability of HA1 measured as the difference in the ΔG
value from that for A/Hong Kong/19/1968 (PDB ID: 2HMG); that is gi = ∑sΔΔGs, where ΔΔGs is the