Ali Mohammad, Emch Michael, von Seidlein Lorenz, Yunus Mohammad, Sack David A, Rao Malla, Holmgren Jan, Clemens John D
International Vaccine Institute, Seoul, Korea.
Lancet. 2005;366(9479):44-9. doi: 10.1016/S0140-6736(05)66550-6.
Decisions about the use of killed oral cholera vaccines, which confer moderate levels of direct protection to vaccinees, can depend on whether the vaccines also provide indirect (herd) protection when high levels of vaccine coverage are attained. We reanalysed data from a field trial in Bangladesh to ascertain whether there is evidence of indirect protection from killed oral cholera vaccines.
We analysed the first year of surveillance data from a placebo-controlled trial of B subunit-killed whole-cell and killed whole-cell-only oral cholera vaccines in children and adult women in Bangladesh. We calculated whether there was an inverse, monotonic trend for the relation between the level of vaccine coverage in a residential cluster and the incidence of cholera in individual vaccine recipients or placebo recipients residing in the cluster after controlling for potential confounding variables.
Vaccine coverage of the targeted population ranged from 4% to 65%. Incidence rates of cholera among placebo recipients were inversely related to levels of vaccine coverage (7.01 cases per 1000 in the lowest quintile of coverage vs 1.47 cases per 1000 in the highest quintile; p<0.0001 for trend). Receipt of vaccine by an individual and the level of vaccine coverage of the individual's cluster were independently related to a reduced risk of cholera. Moreover, after adjustment for the level of vaccine coverage of the cluster, vaccine protective efficacy remained significant (55% [95% CI 41-66], p<0.0001).
In addition to providing direct protection to vaccine recipients, killed oral cholera vaccines confer significant herd protection to neighbouring non-vaccinated individuals. Use of these vaccines could have a major effect on the burden of cholera in endemic settings.
关于使用灭活口服霍乱疫苗的决策，这种疫苗能为接种者提供中等程度的直接保护，这可能取决于在实现高疫苗接种覆盖率时，疫苗是否也能提供间接（群体）保护。我们重新分析了孟加拉国一项现场试验的数据，以确定是否有证据表明灭活口服霍乱疫苗能提供间接保护。
我们分析了在孟加拉国儿童和成年女性中进行的B亚单位 - 灭活全细胞和仅灭活全细胞口服霍乱疫苗安慰剂对照试验的第一年监测数据。在控制潜在混杂变量后，我们计算了居住群组中的疫苗接种覆盖率水平与居住在该群组中的个体疫苗接种者或安慰剂接受者中霍乱发病率之间的关系是否存在反向、单调趋势。
目标人群的疫苗接种覆盖率从4%到65%不等。安慰剂接受者中的霍乱发病率与疫苗接种覆盖率水平呈负相关（覆盖率最低五分位数中每1000人中有7.01例，而最高五分位数中每1000人中有1.47例；趋势p<0.0001）。个体接种疫苗以及个体所在群组的疫苗接种覆盖率水平与霍乱风险降低独立相关。此外，在调整群组的疫苗接种覆盖率水平后，疫苗保护效力仍然显著（55%[95%CI 41 - 66]，p<0.0001）。
除了为疫苗接种者提供直接保护外，灭活口服霍乱疫苗还能为邻近未接种疫苗的个体提供显著的群体保护。使用这些疫苗可能对霍乱流行地区的霍乱负担产生重大影响。
