Herd Protection by a Bivalent Killed Whole-Cell Oral Cholera Vaccine in the Slums of Kolkata, India
Herd Protection by a Bivalent Killed Whole-Cell Oral Cholera Vaccine in the Slums of Kolkata, India
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DOI：
10.1093/cid/cit009
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发表时间：
2013-04-15
影响因子：
11.8
通讯作者：
Clemens, John
中科院分区：
文献类型：
--
作者：
Ali, Mohammad;Sur, Dipika;Clemens, John
背景我们使用2种方法评估了口服霍乱疫苗的群体保护作用：聚类设计和地理信息系统（GIS）设计。居住在印度加尔各答的3933个住宅（集群）的居民被随机分组接受霍乱疫苗或口服安慰剂。年龄>= 1岁的非妊娠居民被邀请参加试验。仅考虑在第二次给药后14至1095天之间检测到受试者的首次霍乱发作。在群设计中，通过比较疫苗群与安慰剂群中非参与者的霍乱发病率来评估间接保护。在GIS分析中，通过评估居住在家庭250 m范围内的人群的疫苗覆盖率与该人群中霍乱发生率之间的关联来评估群体保护。在107347名符合条件的居民中，66990人接受了2剂霍乱疫苗或安慰剂。在群集设计中，3年数据显示显著的总保护（66%保护，95%置信区间[CI]，50%-78%，P < .01），但没有间接保护的证据。采用GIS方法，安慰剂接种者的霍乱风险与社区水平的疫苗覆盖率呈负相关，且趋势非常显著（P <0.01）。这种关系在多变量模型中保持，也控制了潜在的混杂人口统计学变量（风险比，0.94 [95%CI，.90-.98]; P < .01）。间接保护在使用地理信息系统方法的分析中是明显的，但在聚类设计方法中不是，可能是由于霍乱在聚类之间的大量传播，这将损害聚类分析中的牛群保护。
Background. We evaluated the herd protection conferred by an oral cholera vaccine using 2 approaches: cluster design and geographic information system (GIS) design.Methods. Residents living in 3933 dwellings (clusters) in Kolkata, India, were cluster-randomized to receive either cholera vaccine or oral placebo. Nonpregnant residents aged >= 1 year were invited to participate in the trial. Only the first episode of cholera detected for a subject between 14 and 1095 days after a second dose was considered. In the cluster design, indirect protection was assessed by comparing the incidence of cholera among nonparticipants in vaccine clusters vs those in placebo clusters. In the GIS analysis, herd protection was assessed by evaluating association between vaccine coverage among the population residing within 250 m of the household and the occurrence of cholera in that population.Results. Among 107 347 eligible residents, 66 990 received 2 doses of either cholera vaccine or placebo. In the cluster design, the 3-year data showed significant total protection (66% protection, 95% confidence interval [CI], 50%-78%, P < .01) but no evidence of indirect protection. With the GIS approach, the risk of cholera among placebo recipients was inversely related to neighborhood-level vaccine coverage, and the trend was highly significant (P < .01). This relationship held in multivariable models that also controlled for potentially confounding demographic variables (hazard ratio, 0.94 [95%CI, .90-.98]; P < .01).Conclusions. Indirect protection was evident in analyses using the GIS approach but not the cluster design approach, likely owing to considerable transmission of cholera between clusters, which would vitiate herd protection in the cluster analyses.