Data_Sheet_1_Post-vaccination Monitoring to Assess Foot-and-Mouth Disease Immunity at Population Level in Korea.docx

In South Korea, domestic cattle, pigs, and goats were subjected to mandatory foot-and-mouth disease (FMD) vaccination and year-round serosurveillance since 2011. In 2020, approximately USD 95 million was spent solely for FMD vaccine purchase for 59 million livestock, and 1.25 million samples were tested to estimate the population immunity and demonstrate the absence of virus circulation. As the FMD vaccination program was revised in 2018, the post-vaccination monitoring (PVM) was designed to evaluate the effectiveness of the vaccine program of three vaccines approved for routine use. To this end, monitoring post-vaccination immunity has been conducted by collecting 35,626 serum samples at 28 days post-vaccination following regular national vaccinations, which were carried out in April and in October in 2020. The design of the serological test for PVM was specially targeted at particular livestock groups, including dairy cattle, goats, and beef cattle aged 6–12 months, which were generally estimated to have a low expected seroprevalence. The risk factors had also been identified, considering the increased likelihood of infection in a particular location, herd size, and husbandry system applied in a targeted sample collection. Serum sample collection and SP-O and NSP antibody tests were performed by local veterinary laboratories using commercially available ELISAs. The current FMD vaccination program, which was performed twice a year following the regimen of primary vaccination and boost, resulted in over 80% population immunity. The seroprevalence monitored after the vaccination in fall was higher than the one studied in spring except in pigs. It was demonstrated that the seroprevalence of risk-based targeted samples ranged from 93.8 to 100% in cattle, 63.2 to 100% in pigs, and 20.0 to 100% in goats. Of note is the area near the North Korean borders which showed a relatively low seroprevalence among the targeted regions, and no NSP sero-positive reactor was detected in this region. When subpopulation immunity at the individual level was assessed, the seroprevalence in young cattle stock was slightly lower (95.8%) than that of adults (98.4%). In conclusion, the FMD vaccination campaign has been successfully implemented in Korea, and the PVM can be a supplementary program for massive routine surveillance in terms of providing timely information needed both to estimate population immunity and to properly target “risk-based surveillance.”自2011年起，韩国针对家牛、猪与山羊实施强制性口蹄疫（foot-and-mouth disease, FMD）疫苗接种，并开展全年血清学监测。2020年，韩国仅为5900万头畜禽采购口蹄疫疫苗就投入约9500万美元，同时完成125万份样本的检测，用于评估群体免疫水平并验证病毒未发生循环传播。2018年韩国修订口蹄疫免疫计划后，随即建立疫苗后监测（post-vaccination monitoring, PVM）体系，用于评估三款获批用于常规免疫的疫苗的免疫项目效果。为此，研究团队在2020年4月与10月的全国常规免疫接种后第28天，共收集35626份血清样本，以此开展疫苗后免疫监测。本次疫苗后监测的血清学检测专门针对特定畜群：包括6~12月龄的奶牛、山羊和肉牛，这类群体的预期血清阳性率通常较低。本次靶向采样综合考量了特定区域、畜群规模及饲养系统等可能提升感染风险的因素，以此明确相关风险因子。血清样本采集以及结构蛋白O型（structural protein O, SP-O）抗体检测与非结构蛋白（non-structural protein, NSP）抗体检测，均由各地兽医实验室采用商业化酶联免疫吸附试验（ELISA）完成。目前韩国的口蹄疫免疫计划为每年两次，遵循基础免疫与加强免疫的流程，该计划已实现超80%的群体免疫率。除猪群外，秋季免疫后监测得到的血清阳性率均高于春季监测结果。经风险靶向采样的群体血清阳性率范围为：牛群93.8%~100%，猪群63.2%~100%，山羊群20.0%~100%。值得注意的是，朝鲜边境附近区域的血清阳性率在所有靶向监测区域中相对较低，且未在该区域检出非结构蛋白抗体阳性反应动物。在个体层面评估亚群免疫水平时发现，青年牛群的血清阳性率（95.8%）略低于成年牛群（98.4%）。综上，韩国的口蹄疫免疫接种工作已顺利实施，而疫苗后监测体系可作为大规模常规监测的补充手段，在及时提供群体免疫评估所需信息、精准开展风险监测两方面均具有重要应用价值。