Vaccination against colonizing bacteria with multiple serotypes
Vaccination against colonizing bacteria with multiple serotypes
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DOI：
10.1073/pnas.94.12.6571
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发表时间：
1997-06-10
影响因子：
11.1
通讯作者：
Lipsitch, M
中科院分区：
文献类型：
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作者：
Lipsitch, M
结合疫苗可保护接种疫苗的个人免受肺炎链球菌和流感嗜血杆菌的感染和鼻咽部携带疾病的侵袭。由于疫苗中包含的包膜血清型(S)具有特异性保护作用，这种特异性引起了人们的关注，即针对特定(“靶向”)血清型的疫苗接种可能会导致非靶向血清型携带者(和可归因于非靶向血清型的疾病)的增加。我分析了一个数学模型，该模型旨在预测影响宿主人群中这种替换的因素和预期程度，推导出大规模接种下血清型竞争排除和共存的条件，并在各种生态和流行病学条件下确定目标和非目标血清型的平衡载量，在存在竞争的非目标血清型的情况下，特定血清型的目标血清型的根除阈值总是低于双价疫苗，在两个血清型模型中，由于接种任何单一非靶标型的流行率的增加不会超过目标血清型的流行率的总体下降，然而，如果三个或更多的血清型在流行病学上相互作用，针对一种类型的疫苗接种可能会增加第二种类型的携带量，而不是减少第一种类型的携带量，疫苗只对其提供部分保护的第二种血清型的携带量最初可能会增加，然后随着疫苗覆盖率的增加而减少。我讨论了这些理论结果在多大程度上可以解释接种流感嗜血杆菌疫苗后血清型替换的现有数据，以及它们对疫苗政策的影响。
Conjugate vaccines protect vaccinated individuals against both disease from and nasopharyngeal carriage of Streptococcus pneumoniae and Haemophilus influenzae. Protection is specific to the capsular serotype(s) included in the vaccine, This specificity has raised concern that vaccination against particular (''targeted'') serotypes may cause an increase in carriage of (and diseases attributable to) nontargeted serotypes. I analyzed a mathematical model designed to predict the factors affecting, and the expected extent of, such replacement in the host population, The conditions for competitive exclusion and coexistence of serotypes under mass vaccination are derived, and the equilibrium carriage of target and nontarget serotypes is determined under various ecological and epidemiological conditions, The eradication threshold for a target serotype in the presence of competing, nontarget serotypes is always lower for serotype-specific than for bivalent vaccines, In a two-serotype model, the increase in the prevalence of any single nontargeted serotype due to vaccination will not exceed the total reduction in prevalence of a targeted serotype, However, if three or more serotypes interact epidemiologically, vaccination against one type may increase carriage of a second more than it decreases carriage of the first, Carriage of a second serotype against which the vaccine offers only partial protection may initially increase and then decrease as a function of vaccine coverage, I discuss the extent to which these theoretical results can account for existing data on serotype replacement after vaccination against H. influenzae and their implications for vaccine policy.