Figure 3 – figure supplement 2. Excess influenza A(H3N2) mortality increases with H3 and N2 antigenic drift, but correlations are not statistically significant.

The number of excess influenza deaths attributable to A(H3N2) (per 100,000 people) were estimated from a seasonal regression model fit to weekly pneumonia and influenza-coded deaths (Hansen et al., 2022). Seasonal epitope distance is the mean distance between strains circulating in season t and those circulating in the prior season (t − 1) or two seasons ago (t − 2). Distances are scaled to aid in direct comparison of evolutionary indicators. Point color indicates the dominant influenza A subtype based on CDC influenza season summary reports (red: A(H3N2), blue: A(H1N1), purple: A(H1N1)pdm09, orange: A(H3N2)/A(H1N1)pdm09 co-dominant), and vertical bars are 95% confidence intervals of excess mortality estimates. Seasonal national excess mortality estimates were fit as a function of H3 or N2 epitope distance using Gaussian GLMs (log link) with 1000 bootstrap resamples.