Seasonal variation in the age distribution of influenza A cases suggests that factors other than age shape susceptibility to medically attended infection. We ask whether these differences can be partly explained by protection conferred by childhood influenza infection, which has lasting impacts on immune responses to influenza and protection against new influenza A subtypes (phenomena known as original antigenic sin and immune imprinting). Fitting a statistical model to data from studies of influenza vaccine effectiveness (VE), we find that primary infection appears to reduce the risk of medically attended infection with that subtype throughout life. This effect is stronger for H1N1 compared to H3N2. Additionally, we find evidence that VE varies with both age and birth year, suggesting that VE is sensitive to early exposures. Our findings may improve estimates of age-specific risk and VE in similarly vaccinated populations and thus improve forecasting and vaccination strategies to combat seasonal influenza.

中文翻译：

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最早感染预测季节性甲型流感病例的年龄分布

甲型流感病例年龄分布的季节性变化表明，年龄以外的因素会影响就医感染的易感性。我们询问是否可以通过儿童流感感染赋予的保护作用来部分解释这些差异，这对流感的免疫反应和对新甲型流感亚型（称为原始抗原罪和免疫印记的现象）的保护具有持久影响。将统计模型与流感疫苗有效性 (VE) 研究的数据进行拟合，我们发现原发感染似乎可以降低终生因该亚型出现医疗感染的风险。与 H3N2 相比，H1N1 的这种影响更强。此外，我们发现证据表明 VE 随年龄和出生年份而变化，这表明 VE 对早期暴露敏感。