Global Immunization Division, Centers for Disease Control and Prevention, Atlanta, GA, USA.
Centers for Disease Control and Prevention Foundation, Atlanta, GA, USA; Department of Clinical Tropical Medicine, Institute of Tropical Medicine, Nagasaki University Graduate School of Biomedical Science, Nagasaki, Japan.
Lancet Infect Dis. 2024 Jun;24(6):611-618. doi: 10.1016/S1473-3099(23)00809-5. Epub 2024 Feb 6.
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.
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 (PRNT). Participants with a PRNT titre of 10 or higher were considered seropositive. The primary outcome was the proportion of participants seropositive at 5 years.
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.
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.
Gavi, the Vaccine Alliance through the CDC Foundation.
For the French translation of the abstract see Supplementary Materials section.
2016 年，安哥拉和刚果民主共和国爆发的黄热病疫情导致全球疫苗短缺。2016 年 8 月，在刚果民主共和国金沙萨，针对 2 岁及以上儿童和非孕妇成年人（即 18 岁及以上人群），提前开展了大规模疫苗接种运动，使用了 17DD 减毒黄热病疫苗的半量（含标准剂量的五分之一[0.1 毫升]）。接种疫苗 1 年后，97%的参与者血清呈阳性；然而，免疫应答的长期持久性尚不清楚。我们旨在开展一项前瞻性队列研究，并邀请之前评估中入组的参与者在接种疫苗 5 年后返回，以评估免疫应答的持久性。
2021 年，参与者返回金沙萨的 6 个卫生机构之一，研究人员在那里收集了简短的医疗史和血样。我们使用 50%噬斑减少中和试验（PRNT）评估针对黄热病病毒的中和抗体滴度。PRNT 滴度为 10 或更高的参与者被认为血清呈阳性。主要结局为接种 5 年后血清阳性的参与者比例。
在纳入的 764 名参与者中，566 名（74%）完成了 5 年随访。接种疫苗 5 年后，539 名（95.2%，95%CI 93.2-96.7）参与者血清呈阳性，包括 361 名（94.3%，91.5-96.2）初始血清阴性者和 178 名（97.3%，93.8-98.8）初始血清阳性者。对于最初血清阴性者，按年龄组划分，几何平均滴度（GMT）差异显著，GMT 最低的为 2-5 岁年龄组，最高的为 13 岁及以上年龄组。
17DD 黄热病疫苗的半量接种方案在刚果民主共和国的大多数参与者中诱导了免疫应答，可检测到抗体滴度在 5 年时仍存在。这些发现支持使用半量疫苗接种方案来预防疫情爆发，且具有持续免疫的潜力。
全球疫苗免疫联盟通过疾病预防控制中心基金会提供。
