Nanthavong Naphavanh, Black Antony P, Nouanthong Phonethipsavanh, Souvannaso Chanthasone, Vilivong Keooudomphone, Muller Claude P, Goossens Sylvie, Quet Fabrice, Buisson Yves
Institut de la Francophonie pour la Médecine Tropicale, Vientiane, Lao PDR.
Lao-Lux Laboratory, Institut Pasteur du Laos, Vientiane, Lao PDR; Institute of Immunology, Centre de Recherche Public de la Santé / Laboratoire National de Santé, Dudelange, Luxembourg.
PLoS One. 2015 Apr 24;10(4):e0121749. doi: 10.1371/journal.pone.0121749. eCollection 2015.
During late 2012 and early 2013 several outbreaks of diphtheria were notified in the North of the Lao People's Democratic Republic. The aim of this study was to determine whether the re-emergence of this vaccine-preventable disease was due to insufficient vaccination coverage or reduction of vaccine effectiveness within the affected regions.
A serosurvey was conducted in the Huaphan Province on a cluster sampling of 132 children aged 12-59 months. Serum samples, socio-demographic data, nutritional status and vaccination history were collected when available. Anti-diphtheria and anti-tetanus IgG antibody levels were measured by ELISA.
Overall, 63.6% of participants had detectable diphtheria antibodies and 71.2% tetanus antibodies. Factors independently associated with non-vaccination against diphtheria were the distance from the health centre (OR: 6.35 [95% CI: 1.4-28.8], p = 0.01), the Lao Theung ethnicity (OR: 12.2 [95% CI:1,74-85, 4], p = 0.01) and the lack of advice on vaccination given at birth (OR: 9.8 [95% CI: 1.5-63.8], (p = 0.01) while the level of maternal edu-cation was a protective factor (OR: 0.08 [95% CI: 0.008-0.81], p = 0.03). Most respondents claimed financial difficulties as the main reason for non-vaccination. Out of 55 children whose vaccination certificates stated that they were given all 3 doses of diphtheria-containing vaccine, 83.6% had diphtheria antibodies and 92.7% had tetanus antibodies. Furthermore, despite a high prevalence of stunted and underweight children (53% and 25.8%, respectively), the low levels of anti-diphtheria antibodies were not correlated to the nutritional status.
Our data highlight a significant deficit in both the vaccination coverage and diphtheria vaccine effectiveness within the Huaphan Province. Technical deficiencies in the methods of storage and distribution of vaccines as well as unreliability of vaccination cards are discussed. Several hypotheses are advanced to explain such a decline in immunity against diphtheria and recommendations are provided to prevent future outbreaks.
2012年末至2013年初，老挝人民民主共和国北部通报了几起白喉疫情。本研究的目的是确定这种疫苗可预防疾病的再度出现是由于受影响地区疫苗接种覆盖率不足还是疫苗效力下降所致。
在华潘省对132名12 - 59个月大的儿童进行整群抽样血清学调查。收集血清样本、社会人口统计学数据、营养状况和疫苗接种史（如有）。采用酶联免疫吸附测定法检测抗白喉和抗破伤风IgG抗体水平。
总体而言，63.6%的参与者可检测到白喉抗体，71.2%可检测到破伤风抗体。与未接种白喉疫苗独立相关的因素包括与卫生中心的距离（比值比：6.35 [95%置信区间：1.4 - 28.8]，p = 0.01）、老听族裔（比值比：12.2 [95%置信区间：1.74 - 85.4]，p = 0.01）以及出生时未得到疫苗接种建议（比值比：9.8 [95%置信区间：1.5 - 63.8]，p = 0.01），而母亲的教育水平是一个保护因素（比值比：0.08 [95%置信区间：0.008 - 0.81]，p = 0.03）。大多数受访者称经济困难是未接种疫苗的主要原因。在55名疫苗接种证显示已接种全部3剂含白喉疫苗的儿童中，83.6%有白喉抗体，92.7%有破伤风抗体。此外，尽管发育迟缓儿童和体重不足儿童的患病率较高（分别为53%和25.8%），但抗白喉抗体水平低与营养状况无关。
我们的数据突出表明华潘省在疫苗接种覆盖率和白喉疫苗效力方面均存在重大不足。讨论了疫苗储存和分发方法的技术缺陷以及疫苗接种卡的不可靠性。提出了几个假说来解释对白喉免疫力的这种下降，并提供了预防未来疫情爆发的建议。
