Eales Oliver, Shearer Freya M, McCaw James M
Infectious Disease Dynamics Unit, Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia.
School of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia.
PLoS Comput Biol. 2025 Mar 20;21(3):e1012893. doi: 10.1371/journal.pcbi.1012893. eCollection 2025 Mar.
Since its emergence in 1968, influenza A H3N2 has caused yearly epidemics in temperate regions. While infection confers immunity against antigenically similar strains, new antigenically distinct strains that evade existing immunity regularly emerge ('antigenic drift'). Immunity at the individual level is complex, depending on an individual's lifetime infection history. An individual's first infection with influenza typically elicits the greatest response with subsequent infections eliciting progressively reduced responses ('antigenic seniority'). The combined effect of individual-level immune responses and antigenic drift on the epidemiological dynamics of influenza are not well understood. Here we develop an integrated modelling framework of influenza transmission, immunity, and antigenic drift to show how individual-level exposure, and the build-up of population level immunity, shape the long-term epidemiological dynamics of H3N2. Including antigenic seniority in the model, we observe that following an initial decline after the pandemic year, the average annual attack rate increases over the next 80 years, before reaching an equilibrium, with greater increases in older age-groups. Our analyses suggest that the average attack rate of H3N2 is still in a growth phase. Further increases, particularly in the elderly, may be expected in coming decades, driving an increase in healthcare demand due to H3N2 infections.
自1968年出现以来，甲型H3N2流感每年都会在温带地区引发疫情。虽然感染会产生针对抗原相似毒株的免疫力，但能逃避现有免疫力的新的抗原不同毒株会定期出现（“抗原漂移”）。个体层面的免疫力很复杂，取决于个体一生的感染史。个体首次感染流感通常会引发最大反应，后续感染引发的反应会逐渐减弱（“抗原资深性”）。个体层面免疫反应和抗原漂移对流感流行病学动态的综合影响尚未得到很好的理解。在此，我们开发了一个流感传播、免疫和抗原漂移的综合建模框架，以展示个体层面的接触以及人群层面免疫力的积累如何塑造H3N2的长期流行病学动态。在模型中纳入抗原资深性后，我们观察到在大流行年份后的最初下降之后，平均年发病率在接下来的80年里会上升，然后达到平衡，老年人群体的上升幅度更大。我们的分析表明，H3N2的平均发病率仍处于增长阶段。预计在未来几十年中，发病率还会进一步上升，尤其是在老年人中，这将导致因H3N2感染而产生的医疗需求增加。
