Abstract：
BACKGROUND: In 2016, outbreaks of yellow fever in Angola and the Democratic Republic of the Congo led to a global vaccine shortage. A fractional dose of 17DD yellow fever vaccine (containing one-fifth [0·1 ml] of the standard dose) was used during a pre-emptive mass campaign in August, 2016, in Kinshasa, Democratic Republic of the Congo among children aged 2 years and older and non-pregnant adults (ie, those aged 18 years and older). 1 year following vaccination, 97% of participants were seropositive; however, the long-term durability of the immune response is unknown. We aimed to conduct a prospective cohort study and invited participants enrolled in the previous evaluation to return 5 years after vaccination to assess durability of the immune response.
METHODS: Participants returned to one of six health facilities in Kinshasa in 2021, where study staff collected a brief medical history and blood specimen. We assessed neutralising antibody titres against yellow fever virus using a plaque reduction neutralisation test with a 50% cutoff (PRNT50). Participants with a PRNT50 titre of 10 or higher were considered seropositive. The primary outcome was the proportion of participants seropositive at 5 years.
RESULTS: Among the 764 participants enrolled, 566 (74%) completed the 5-year visit. 5 years after vaccination, 539 (95·2%, 95% CI 93·2-96·7) participants were seropositive, including 361 (94·3%, 91·5-96·2) of 383 who were seronegative and 178 (97·3%, 93·8-98·8) of 183 who were seropositive at baseline. Geometric mean titres (GMTs) differed significantly across age groups for those who were initially seronegative with the lowest GMT among those aged 2-5 years and highest among those aged 13 years and older.
CONCLUSIONS: A fractional dose of the 17DD yellow fever vaccine induced an immunologic response with detectable titres at 5 years among the majority of participants in the Democratic Republic of the Congo. These findings support the use of fractional-dose vaccination for outbreak prevention with the potential for sustained immunity.
BACKGROUND: Gavi, the Vaccine Alliance through the CDC Foundation.
UNASSIGNED: For the French translation of the abstract see Supplementary Materials section.
METHODS: Participants returned to one of six health facilities in Kinshasa in 2021, where study staff collected a brief medical history and blood specimen. We assessed neutralising antibody titres against yellow fever virus using a plaque reduction neutralisation test with a 50% cutoff (PRNT50). Participants with a PRNT50 titre of 10 or higher were considered seropositive. The primary outcome was the proportion of participants seropositive at 5 years.
RESULTS: Among the 764 participants enrolled, 566 (74%) completed the 5-year visit. 5 years after vaccination, 539 (95·2%, 95% CI 93·2-96·7) participants were seropositive, including 361 (94·3%, 91·5-96·2) of 383 who were seronegative and 178 (97·3%, 93·8-98·8) of 183 who were seropositive at baseline. Geometric mean titres (GMTs) differed significantly across age groups for those who were initially seronegative with the lowest GMT among those aged 2-5 years and highest among those aged 13 years and older.
CONCLUSIONS: A fractional dose of the 17DD yellow fever vaccine induced an immunologic response with detectable titres at 5 years among the majority of participants in the Democratic Republic of the Congo. These findings support the use of fractional-dose vaccination for outbreak prevention with the potential for sustained immunity.
BACKGROUND: Gavi, the Vaccine Alliance through the CDC Foundation.
UNASSIGNED: For the French translation of the abstract see Supplementary Materials section.
摘要：
背景：2016年，安哥拉和刚果民主共和国爆发黄热病导致全球疫苗短缺。在8月份的先发制人的大规模运动中，使用了部分剂量的17DD黄热病疫苗（包含标准剂量的五分之一[0·1ml]），2016年，在金沙萨，刚果民主共和国2岁及以上儿童和非怀孕成年人(即，18岁及以上)。接种疫苗1年后，97%的参与者是血清阳性;然而,免疫反应的长期持久性是未知的。我们旨在进行一项前瞻性队列研究，并邀请参加先前评估的参与者在疫苗接种后5年返回，以评估免疫反应的持久性。
方法：参与者于2021年返回金沙萨的六个医疗机构之一，研究人员在那里收集了简短的病史和血液样本。我们使用具有50％截止值（PRNT50）的空斑减少中和试验评估了针对黄热病病毒的中和抗体滴度。PRNT50滴度为10或更高的参与者被认为是血清阳性。主要结果是5年时参与者血清阳性的比例。
结果：在764名参与者中，566（74％）完成了为期5年的访问。接种疫苗后5年，539（95·2%，95%CI93·2-96·7)参与者血清呈阳性，包括361（94·3%，91·5-96·2）383名血清阴性者和178名（97·3%，93·8-98·8）的183名基线血清阳性。对于最初为血清阴性的患者，2-5岁的GMT最低，13岁及以上的GMT最高的患者，几何平均滴度（GMT）在不同年龄段之间存在显着差异。
结论：在刚果民主共和国的大多数参与者中，部分剂量的17DD黄热病疫苗在5年时诱导了可检测滴度的免疫应答。这些发现支持使用分剂量疫苗预防爆发，并具有持续免疫的潜力。
背景：Gavi，通过CDC基金会的疫苗联盟。
■有关摘要的法语翻译，请参见补充材料部分。
方法：参与者于2021年返回金沙萨的六个医疗机构之一，研究人员在那里收集了简短的病史和血液样本。我们使用具有50％截止值（PRNT50）的空斑减少中和试验评估了针对黄热病病毒的中和抗体滴度。PRNT50滴度为10或更高的参与者被认为是血清阳性。主要结果是5年时参与者血清阳性的比例。
结果：在764名参与者中，566（74％）完成了为期5年的访问。接种疫苗后5年，539（95·2%，95%CI93·2-96·7)参与者血清呈阳性，包括361（94·3%，91·5-96·2）383名血清阴性者和178名（97·3%，93·8-98·8）的183名基线血清阳性。对于最初为血清阴性的患者，2-5岁的GMT最低，13岁及以上的GMT最高的患者，几何平均滴度（GMT）在不同年龄段之间存在显着差异。
结论：在刚果民主共和国的大多数参与者中，部分剂量的17DD黄热病疫苗在5年时诱导了可检测滴度的免疫应答。这些发现支持使用分剂量疫苗预防爆发，并具有持续免疫的潜力。
背景：Gavi，通过CDC基金会的疫苗联盟。
■有关摘要的法语翻译，请参见补充材料部分。
