Department of Infection and Immunity, Luxembourg Institute of Health, Esch-sur-Alzette, Grand-Duchy of Luxembourg.
New Vaccines, Murdoch Children's Research Institute, Parkville, Victoria, Australia.
PLoS One. 2022 Sep 15;17(9):e0274558. doi: 10.1371/journal.pone.0274558. eCollection 2022.
Vaccination has dramatically reduced invasive Haemophilus influenzae type b (Hib) disease worldwide. Hib vaccination was introduced in the Lao PDR in 2009, as part of the pentavalent vaccine. To contribute to the understanding of the epidemiology of Hib in Lao PDR and the protection levels before and after the introduction of the vaccination, we tested serum samples from existing cohorts of vaccine age-eligible children and unvaccinated adolescents for antibodies against Hib.
Serum samples from 296 adolescents born before vaccine introduction and from 1017 children under 5 years (vaccinated and unvaccinated) were tested for anti-Hib antibodies by ELISA. Bivariate analyses were performed to investigate factors associated with long-term protection.
The vast majority of all participants showed evidence of short- (42.7%) or long-term (56.1%) protection against Hib. Almost all of the unvaccinated adolescents had antibody titers indicating short-term protection and almost half (45.6%) were long-term protected. Nearly all children (>99.0%) were at least short-term protected, even those that were unvaccinated or whose vaccination status was unknown. Among vaccinated children, participants vaccinated more than 1 or 2 years ago and with a mid-upper arm circumference z-score < -2 were less likely to be long-term protected.
Nearly all adolescents born before the introduction of Hib vaccination in the Lao PDR had antibody titers corresponding to at least short-term protection, indicating a high burden of Hib disease at that time. After vaccine introduction, all but four children (>99%) showed at least short-term protection. Possible explanations for the proportion of protected, yet apparently unvaccinated children, may be past infections, cross-reacting antibodies or faulty vaccination documentation. Our results highlight the need for robust surveillance and reporting of invasive Hib disease to determine the burden of disease despite vaccination.
疫苗接种已在全球范围内显著降低了侵袭性流感嗜血杆菌 b 型（Hib）疾病的发病率。2009 年，老挝人民民主共和国将 Hib 疫苗纳入五联疫苗，作为其中的一部分。为了更好地了解老挝人民民主共和国 Hib 的流行病学和疫苗接种前后的保护水平，我们对现有疫苗接种年龄组儿童和未接种青少年的血清样本进行了 Hib 抗体检测。
通过酶联免疫吸附试验（ELISA）检测了 296 名出生于疫苗引入前的青少年和 1017 名 5 岁以下儿童（接种和未接种）的血清样本中针对 Hib 的抗体。采用双变量分析来调查与长期保护相关的因素。
绝大多数参与者都表现出对 Hib 的短期（42.7%）或长期（56.1%）保护。几乎所有未接种的青少年都有短期保护的抗体滴度，近一半（45.6%）具有长期保护。几乎所有儿童（>99.0%）都至少有短期保护，即使他们未接种或其接种状态未知。在接种疫苗的儿童中，接种疫苗超过 1 年或 2 年且上臂中部周长 z 评分< -2 的儿童不太可能具有长期保护。
在老挝人民民主共和国 Hib 疫苗引入之前出生的几乎所有青少年都具有至少短期保护的抗体滴度，这表明当时 Hib 疾病负担很高。疫苗引入后，除了四名儿童（>99%）外，所有儿童都至少具有短期保护。对于那些有保护作用但显然未接种疫苗的儿童的比例，可能的解释是既往感染、交叉反应抗体或疫苗接种记录错误。我们的结果强调需要进行强有力的监测和报告侵袭性 Hib 疾病，以确定疫苗接种后的疾病负担。
