Institute of Technology for Immunobiologicals of Bio-Manguinhos/FIOCRUZ, Brazil.
Institute of Technology for Immunobiologicals of Bio-Manguinhos/FIOCRUZ, Brazil.
Vaccine. 2019 Nov 15;37(48):7147-7154. doi: 10.1016/j.vaccine.2019.09.051. Epub 2019 Oct 4.
Vaccination is the most important measure for prevention and control of yellow fever. It is recommended by the World Health Organization (WHO) for residents of endemic areas and travelers to risk areas. In 2013, the WHO discontinued the recommendation of booster doses every 10 years, indicating a single dose as sufficient for lifelong protection.
Considering the lower immune response to YF vaccine in children compared to adults, this study was set out to assess the duration of immunity to YF in children vaccinated in the first two years of life.
This cross-sectional study involved children aged 9 months to 12 years with accessible vaccination records recruited in primary care units from a metropolitan area in Southeast Brazil. The serologic status (negative, indeterminate and positive), and geometric mean titers (GMT, inverse dilution) of neutralizing antibodies against YF obtained by Plaque Reduction Neutralization Test was assessed across categories of time after YF vaccination. The strength of association of seropositivity with time was assessed by the odds ratio (OR) taking recent vaccination (1-6 months) as reference.
A total of 824 children recruited from August 2010 to July 2011were tested. The proportion of seropositivity (95% C.I.) and GMT (95% C.I.) dropped markedly across time periods: from 86.7% (80.5-91.4%), GMT 47.9 (38.3-59.9) in newly vaccinated to 59.0% (49.7-67.8%), GMT 14.8 (11.6-19.1) and 42.2% (33.8-51.0), GMT 8.6 (7.1-12.1), respectively in the subgroups vaccinated 31-72 months and 73-100 months before.
Analogous to previous findings in adults, these data support the need for revaccination of children living in areas with yellow fever virus circulation in humans or in other primates. The data also supported the change of a booster dose to 4 years of age for those primarily vaccinated for yellow fever in the first two years of life.
接种疫苗是预防和控制黄热病的最重要措施。世界卫生组织（WHO）建议居住在流行地区的居民和前往风险地区的旅行者接种疫苗。2013 年，世卫组织停止了每 10 年加强剂量的建议，表明单次剂量足以提供终身保护。
鉴于儿童对黄热病疫苗的免疫反应较低，与成年人相比，本研究旨在评估在生命的头两年接种黄热病疫苗的儿童的免疫持久性。
这项横断面研究涉及了在巴西东南部大都市地区的基层医疗单位招募的 9 个月至 12 岁、可获取疫苗接种记录的儿童。通过蚀斑减少中和试验评估了针对黄热病的中和抗体的血清学状态（阴性、不确定和阳性）和几何平均滴度（GMT，倒数稀释），并按黄热病疫苗接种后时间的类别进行了评估。以近期（1-6 个月）接种疫苗为参考，用优势比（OR）评估血清阳性与时间的关联强度。
2010 年 8 月至 2011 年 7 月期间共招募了 824 名儿童进行测试。血清阳性率（95%CI）和 GMT（95%CI）随时间显著下降：从新接种疫苗的 86.7%（80.5-91.4%）和 47.9（38.3-59.9）降至 31-72 个月和 73-100 个月前接种疫苗的 59.0%（49.7-67.8%）和 14.8（11.6-19.1）和 8.6（7.1-12.1）。
与之前在成年人中的发现类似，这些数据支持在人类或其他灵长类动物中存在黄热病病毒循环的地区为儿童进行复种。这些数据还支持将加强剂量改为 4 岁，以取代那些在生命的头两年接种黄热病疫苗的儿童。
