Figure 1. Seasonal influenza vaccine effectiveness in the US as estimated by the Centers for Disease Control and Prevention (CDC) [15,16,17,18,19,20,21,22,23,24,25]. (a) Proportions of identified virus types, subtypes, and lineages by year. (b) Adjusted vaccine effectiveness for influenza A strains. (c) Adjusted vaccine effectiveness for influenza B strains. (d) Adjusted overall seasonal effectiveness. Error bars for (b–d) indicate adjusted 95% confidence interval. ND, no data. Figure 1. Seasonal influenza vaccine effectiveness in the US as estimated by the Centers for Disease Control and Prevention (CDC) [15,16,17,18,19,20,21,22,23,24,25]. (a) Proportions of identified virus types, subtypes, and lineages by year. (b) Adjusted vaccine effectiveness for influenza A strains. (c) Adjusted vaccine effectiveness for influenza B strains. (d) Adjusted overall seasonal effectiveness. Error bars for (b–d) indicate adjusted 95% confidence interval. ND, no data. Figure 2. CDC-adjusted overall vaccine effectiveness estimates and documented A/H3N2 antigenic match or mismatch each season, as shown in Figure 1 (top), with numbers of US hospitalizations (middle) and deaths (bottom) due to influenza [15,16,17,18,19,20,21,22,23,24,26,27,28,29]. Figure 3. Influenza HA protein is a heterodimer comprising HA1 (turquoise) and HA2 (orange) linked though an inter-disulfide (S–S) bond and containing complex-type sialylated N-linked glycans. Cleaved fusion peptides (green) eliminate unique HA epitopes, and complex glycans mask unique epitopes on HA. Modified and reprinted with permission from Arunachalam et al. NPJ Vaccines 2021;6:144 [65]. Creative commons license: https://creativecommons.org/licenses/by/4.0/, accessed on 1 October 2022. Table 1. Comparison of sequence data for HA and NA isolated from virus samples obtained at different stages in the manufacturing process [38] a. Table 1. Comparison of sequence data for HA and NA isolated from virus samples obtained at different stages in the manufacturing process [38] a. Influenza Virus TypeOCS vs. MDCK bOCS/MDCK vs. WVS bHANAHANAA/H1N15/5 identical5/5 identical4/5 identical c5/5 identicalA/H3N25/5 identical4/5 identical d5/5 identical5/5 identicalB/Victoria2/2 identical2/2 identical3/3 identical3/3 identicalB/Yamagata1/1 identical1/1 identical1/1 identical1/1 identical