In this paper we introduce a single serotype transmission model, including an age-dependent mosquito biting rate, to find the optimal vaccination age against dengue in Brazil with Dengvaxia. The optimal vaccination age and minimal lifetime expected risk of hospitalisation are found by adapting a method due to Hethcote (Math Biosci 89:29–52). Any number and combination of the four dengue serotypes DENv1–4 is considered. Successful vaccination against a serotype corresponds to a silent infection. The effects of antibody-dependent enhancement (ADE) and permanent cross-immunity after two heterologous infections are studied. ADE is assumed to imply risk-free primary infections, while permanent cross-immunity implies risk-free tertiary and quaternary infections. Data from trials of Dengvaxia indicate vaccine efficacy to be age and serostatus dependent and vaccination of seronegative individuals to induce an increased risk of hospitalisation. Some of the scenarios are therefore reconsidered taking these findings into account. The optimal vaccination age is compared to that achievable under the current age restriction of the vaccine. If vaccination is not considered to induce risk, optimal vaccination ages are very low. The assumption of ADE generally leads to a higher optimal vaccination age in this case. For a single serotype vaccination is not recommended in the case of ADE. Permanent cross-immunity results in a slightly lower optimal vaccination age. If vaccination induces a risk, the optimal vaccination ages are much higher, particularly for permanent cross-immunity. ADE has no effect on the optimal vaccination age when permanent cross-immunity is considered; otherwise, it leads to a slight increase in optimal vaccination age.

中文翻译：

---

登革热疫苗接种的最佳年龄与年龄相关的叮咬率在巴西的应用

在本文中，我们介绍了一种单一血清型传播模型，包括与年龄相关的蚊虫叮咬率，以寻找在巴西登革热疫苗接种登革热的最佳疫苗接种年龄。通过采用 Hethcote (Math Biosci 89:29–52) 的方法，可以找到最佳疫苗接种年龄和最小的终生预期住院风险。考虑四种登革热血清型 DENv1-4 的任意数量和组合。针对血清型的成功接种对应于无声感染。研究了两种异源感染后抗体依赖性增强 (ADE) 和永久交叉免疫的影响。假设 ADE 意味着无风险的初级感染，而永久性交叉免疫意味着无风险的三级和四级感染。来自 Dengvaxia 试验的数据表明疫苗效力取决于年龄和血清状态，并且对血清阴性个体进行疫苗接种会导致住院风险增加。因此，考虑到这些发现，重新考虑了一些情景。将最佳疫苗接种年龄与当前疫苗年龄限制下可达到的接种年龄进行比较。如果认为接种疫苗不会诱发风险，则最佳接种年龄非常低。在这种情况下，ADE 的假设通常会导致更高的最佳疫苗接种年龄。对于 ADE，不建议接种单一血清型疫苗。永久性交叉免疫导致最佳疫苗接种年龄略低。如果疫苗接种会引起风险，则最佳接种年龄要高得多，特别是对于永久性交叉免疫。当考虑永久交叉免疫时，ADE对最佳接种年龄没有影响；否则，它会导致最佳疫苗接种年龄略有增加。