Departament of Epidemiology and Quantitative Methods in Health, Escola Nacional de Saúde Pública, FIOCRUZ, Rua Leopoldo Bulhões, 1480, Sala 803. Manguinhos, Rio de Janeiro-RJ 21041-210, Brazil.
Vaccine. 2019 Aug 14;37(35):5129-5135. doi: 10.1016/j.vaccine.2019.05.048. Epub 2019 Jun 3.
Antibody levels following yellow fever vaccination (YFV) decrease considerably with time, leaving a substantial proportion of single-dose recipients seronegative after 10 years. Little is known about the persistence of immunity after two or more doses of the vaccine. This study was designed to verify the current immune status of adults who had received two or more doses of YFV. A cross-sectional study assessed the immune status for yellow fever according to time since the latest YFV: second dose at 30-45 days (reference group), 1-5 years, 6-9 years and 10 years or more; and three or more doses. Volunteers had their vaccination cards checked and were interviewed before having a blood sample drawn for titration of neutralizing YF antibodies, and being tested for dengue IgG. The proportion seropositive (titer ≥ 1:50) and the geometric mean titers (GMT) were compared among the subgroups of time since the latest YFV. Participants (n = 323) were predominantly female (80.5%) and had a median age of 34 years (range 18-76). In the reference group (n = 99), 69% were seropositive before the second dose. After revaccination, the proportions seropositive (95% C.I.) were 100% (96-100%) in the reference subgroup, 90% (83-95%) in the 1-5 year subgroup (n = 109), 86% (77-92%) in the 6-9 year subgroup (n = 92) and 86% (57-98%) in the 10+ years subgroup (n = 14). Only 9 participants with more than 2 previous doses of YFV were eligible for the study, and 8 of them were seropositive. Sociodemographic variables, age at vaccination and previous dengue infection did not confound the association of seropositivity to time since the last YFV. The results support the need of booster doses of the YFV to maintain antibody levels consistent with protection, and indicate that a small proportion of individuals may need more than two doses, provided that priority is given to primovaccination of all susceptibles.
接种黄热病疫苗（YFV）后，抗体水平会随时间显著下降，10 年后，相当一部分单剂接种者血清学呈阴性。对于疫苗接种两剂或更多剂后的免疫持久性知之甚少。本研究旨在验证曾接种两剂或更多剂 YFV 的成年人的当前免疫状态。一项横断面研究根据距最后一剂 YFV 的时间评估了黄热病的免疫状态：第二剂在 30-45 天（参考组）、1-5 年、6-9 年和 10 年或以上；以及三剂或更多剂。志愿者在采血进行中和性 YF 抗体滴度测定和检测登革热 IgG 之前，检查了疫苗接种卡并接受了访谈。比较了距最后一剂 YFV 的时间的亚组中血清阳性率（滴度≥1:50）和几何平均滴度（GMT）。参与者（n=323）主要为女性（80.5%），中位年龄为 34 岁（范围 18-76 岁）。在参考组（n=99）中，69%的人在第二剂之前呈血清阳性。再次接种疫苗后，参考亚组的血清阳性率（95%CI）为 100%（96-100%），1-5 年亚组为 90%（83-95%）（n=109），6-9 年亚组为 86%（77-92%）（n=92），10+年亚组为 86%（57-98%）（n=14）。只有 9 名有两剂以上 YFV 既往接种史的参与者符合研究条件，其中 8 名血清阳性。社会人口统计学变量、接种年龄和既往登革热感染并未影响血清阳性与距最后一剂 YFV 时间的关联。结果支持 YFV 加强剂量以维持与保护一致的抗体水平的必要性，并表明少数人可能需要两剂以上的剂量，前提是优先对所有易感者进行初免。
