Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615N. Wolfe St., Baltimore, MD 21201, USA.
Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615N. Wolfe St., Baltimore, MD 21201, USA.
Vaccine. 2014 Feb 12;32(8):944-8. doi: 10.1016/j.vaccine.2013.12.052. Epub 2014 Jan 4.
Herd protection of Haemophilus influenzae type b (Hib) conjugate vaccine has been associated with excessive decrease of invasive Hib diseases, i.e., pneumonia and meningitis, with increased national or regional Hib vaccine coverage. Only a few studies have examined herd protection at the individual level and even less evidence is available from Asia. We examined Hib vaccine herd protection against radiologically confirmed pneumonia among children less than 2 years old.
We incorporated data from a matched case-control study and a vaccine coverage survey in Dhaka, Bangladesh. Pneumonia cases (n=343) were confirmed by radiology. For each case, two controls with conditions other than pneumonia or meningitis were selected from the same hospital. Hib vaccine coverage was calculated as percentages of children who received at least 2 doses of Hib vaccine from a survey in the neighborhood centered on each case and control. Conditional logistic regression was fit to examine the association between vaccine coverage and risk of radiologically confirmed pneumonia.
Neighborhood Hib vaccine coverage varied from 0% to 63.5% for cases and from 8.7% to 61.5% for controls, respectively. Cases were less likely to have neighborhood coverage higher than 20% (OR=0.49, 0.52, 0.55, and 0.69 for coverage 20-29%, 30-39%, 40-49%, and ≥50%, respectively) than coverage <20%, compared to controls, although the estimates for coverage 40-49% and ≥50% were not statistically significant.
The study indicates that Hib vaccine may provide herd protection, even when the coverage is as low as 20-39%, in a low-income country. Asian countries should consider herd protection in implementing effective vaccine policy with limited resources.
乙型流感嗜血杆菌（Hib）结合疫苗的群体保护作用与侵袭性 Hib 疾病（即肺炎和脑膜炎）的过度减少有关，这与全国或地区 Hib 疫苗覆盖率的提高有关。只有少数研究检查了个体层面的群体保护作用，来自亚洲的证据则更少。我们研究了 Hib 疫苗对 2 岁以下儿童放射学确诊肺炎的群体保护作用。
我们整合了孟加拉国达卡的一项匹配病例对照研究和疫苗覆盖率调查的数据。肺炎病例（n=343）通过放射学确诊。对于每个病例，从同一医院选择两名患有肺炎或脑膜炎以外疾病的对照。根据在每个病例和对照所在的以社区为中心的调查，计算 Hib 疫苗覆盖率，即至少接受 2 剂 Hib 疫苗的儿童比例。使用条件逻辑回归来检验疫苗覆盖率与放射学确诊肺炎风险之间的关联。
病例所在社区的 Hib 疫苗覆盖率为 0%-63.5%，而对照所在社区的覆盖率为 8.7%-61.5%。与对照相比，病例所在社区的覆盖率高于 20%的可能性较小（覆盖率 20-29%、30-39%、40-49%和≥50%的 OR 值分别为 0.49、0.52、0.55 和 0.69），尽管覆盖率 40-49%和≥50%的估计值没有统计学意义。
该研究表明，即使在低收入国家，Hib 疫苗的覆盖率低至 20-39%，也可能提供群体保护作用。亚洲国家在实施资源有限的有效疫苗政策时，应考虑群体保护作用。
