Long-term immunity against yellow fever in children vaccinated during infancy: a longitudinal cohort study
Long-term immunity against yellow fever in children vaccinated during infancy: a longitudinal cohort study
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DOI：
10.1016/s1473-3099(19)30323-8
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发表时间：
2019-12-01
影响因子：
56.3
通讯作者：
Mejia, Jose E.
中科院分区：
文献类型：
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作者：
Domingo, Cristina;Fraissinet, Juliane;Mejia, Jose E.
背景根据扩大免疫方案，9-12个月的婴儿常规接种单剂黄热病疫苗，但这一年龄段的疫苗接种的长期结果尚不清楚。我们的目的是评估在婴儿常规接种黄热病病毒疫苗后，黄热病病毒中和抗体的长期持久性。方法我们进行了纵向队列研究，使用微中和试验检测接种后9个月左右的马里和加纳儿童对黄热病的保护性抗体，并随访了4.5年(马里)或2.3年和6.0年(加纳)。包括有第0天血清可用、有完整随访史、没有黄热病复种记录的健康儿童；排除基线黄热病血清阳性的儿童。我们参照世界卫生组织黄热病国际标准对抗体浓度进行了标准化。我们发现有587名马里儿童和436名加纳儿童在2009年6月5日至2012年12月26日期间接种了疫苗。在马里组中，296例(50.4%，95%可信区间46.4~54.5)在免疫后4.5年呈抗体阳性(抗体浓度=0.5IU/mL)。在加纳儿童中，有121人(27.8%，23.5-32.0)在2.3岁后血清阳性。这些结果表明，接种疫苗后28天血清阳性婴儿的比例大幅下降，马里为96.7%，加纳为72.7%，这是先前对两个研究人群进行的研究报告的结果。在加纳组，接种疫苗6.0年后，血清阳性儿童的数量增加到188人(43.1%，95%可信区间38.5-47.8)，但这一结果可能会被2011-12年加纳北部暴发期间无记录的重新接种或自然感染野生黄热病病毒所混淆。解释在9个月大的婴儿接种疫苗后早期几年免疫迅速减弱的情况表明，在流行国家修订针对这一目标人群的单剂建议。许多接种者的免疫持续时间很短，这表明有必要加强接种，以达到预防黄热病暴发的80%人群免疫阈值。
Background A single dose of vaccine against yellow fever is routinely administered to infants aged 9-12 months under the Expanded Programme on Immunization, but the long-term outcome of vaccination in this age group is unknown. We aimed to evaluate the long-term persistence of neutralising antibodies to yellow fever virus following routine vaccination in infancy.Methods We did a longitudinal cohort study, using a microneutralisation assay to measure protective antibodies against yellow fever in Malian and Ghanaian children vaccinated around age 9 months and followed up for 4.5 years (Mali), or 2.3 and 6.0 years (Ghana). Healthy children with available day-0 sera, a complete follow-up history, and no record of yellow fever revaccination were included; children seropositive for yellow fever at baseline were excluded. We standardised antibody concentrations with reference to the yellow fever WHO International Standard.Findings We included 587 Malian and 436 Ghanaian children vaccinated between June 5, 2009, and Dec 26, 2012. In the Malian group, 296 (50.4%, 95% CI 46.4-54.5) were seropositive (antibody concentration >= 0.5 IU/mL) 4.5 years after vaccination. Among the Ghanaian children, 121 (27.8%, 23.5-32.0) were seropositive after 2.3 years. These results show a large decrease from the proportions of seropositive infants 28 days after vaccination, 96.7% in Mali and 72.7% in Ghana, reported by a previous study of both study populations. The number of seropositive children increased to 188 (43.1%, 95% CI 38.5-47.8) in the Ghanaian group 6.0 years after vaccination, but this result might be confounded by unrecorded revaccination or natural infection with wild yellow fever virus during a 2011-12 outbreak in northern Ghana.Interpretation Rapid waning of immunity during the early years after vaccination of 9-month-old infants argues for a revision of the single-dose recommendation for this target population in endemic countries. The short duration of immunity in many vaccinees suggests that booster vaccination is necessary to meet the 80% population immunity threshold for prevention of yellow fever outbreaks.