Department of Haematology, Reference Centre of Sickle Cell Disease, Hôpital Robert Debré, APHP, 48 Bd Sérurier, Paris 75019, France.
Université de Paris, 48 Bld Serurier, 75019, Paris, France.
J Travel Med. 2021 Apr 14;28(3). doi: 10.1093/jtm/taab013.
Sickle cell disease (SCD) children are frequent travellers to countries where yellow fever (YF) is endemic, but there are no data regarding the safety and immunogenicity of the vaccine in such children treated with hydroxyurea (HU). The main objective of this study was to compare the tolerance and immune response to YF vaccination in SCD children treated or not with HU.
SCD children < 18 years attending the international travel clinics of three large paediatric centres and requiring a first YF vaccination were included in a prospective study. Adverse events were collected 2 weeks after vaccination. YF vaccine antibody titres were measured ~6 months after vaccination.
Among the 52 SCD children vaccinated against YF, 17 (33%) were treated with HU. Only mild adverse events, mainly fever and local reaction, were observed in the HU group with a similar frequency in the non-HU group (57 and 35%, respectively, P = 0.30). YF antibody titres were measured in 15/17 patients in the HU group and 23/35 patients in the non-HU group after a median of 6.0 months (3.5-8.5) following vaccination. The geometric mean of YF antibody titre was similar in both groups. A protective antibody level was observed in 85% of the children in the HU group vs 100% in the non-HU group (P = 0.14), suggesting a lower effectiveness of the vaccine in patients on HU similarly to what has been described in patients on immune suppressive therapy for other vaccines.
YF vaccination seems to be safe and efficient in SCD children treated with HU. Considering the potential risk of severe complications in cases of YF while travelling in Africa for those patients, the benefit-to-risk ratio argues for YF vaccination in all SCD children. Control of a protective antibody titre may also be useful to ascertain an adequate response in those treated with HU.
镰状细胞病（SCD）患儿经常前往黄热病（YF）流行的国家旅行，但目前尚无关于羟基脲（HU）治疗的此类儿童接种 YF 疫苗的安全性和免疫原性的数据。本研究的主要目的是比较 HU 治疗或未治疗的 SCD 儿童接种 YF 疫苗的耐受性和免疫反应。
纳入了在三个大型儿科中心的国际旅行诊所就诊且需要首次 YF 疫苗接种的 <18 岁的 SCD 患儿，并进行了前瞻性研究。接种后 2 周收集不良反应。接种后约 6 个月测量 YF 疫苗抗体滴度。
在接种 YF 的 52 名 SCD 患儿中，有 17 名（33%）接受 HU 治疗。HU 组仅观察到轻度不良反应，主要为发热和局部反应，与非 HU 组的频率相似（分别为 57%和 35%，P=0.30）。在 HU 组中，有 15/17 例患者和非 HU 组中 23/35 例患者在接种后中位数 6.0 个月（3.5-8.5）后测量了 YF 抗体滴度。两组 YF 抗体滴度的几何均数相似。HU 组中 85%的儿童出现保护性抗体水平，而非 HU 组中为 100%（P=0.14），提示 HU 治疗的儿童中疫苗的有效性较低，这与其他疫苗免疫抑制治疗的患者中描述的情况类似。
HU 治疗的 SCD 儿童接种 YF 疫苗似乎是安全有效的。考虑到这些患儿在非洲旅行时感染 YF 可能导致严重并发症的潜在风险，对于所有 SCD 患儿而言，接种 YF 疫苗的获益风险比是合理的。控制保护性抗体滴度也可能有助于确定 HU 治疗的患儿的适当反应。
