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Background: 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., Method: 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., Results: 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., Conclusion: 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., (© International Society of Travel Medicine 2021. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Pulmonary embolism is a life-threatening and potentially lethal disease. Its incidence in children with sickle cell disease is probably underestimated and pediatric case reports in the literature are rare. Moreover, symptoms can mimic an acute chest syndrome. We report on the case of a 17-year-old boy with SS sickle cell disease, admitted for chest pain with dyspnea and tachycardia. Pulmonary angiography revealed a partial bilateral obstructive pulmonary embolism. We did not find any deep venous thrombosis or thrombophilia. The progression was rapidly favorable with anticoagulant therapy. We recommend a pulmonary angiography for any chest pain that does not evolve favorably in a child with sickle cell disease. Large series of pediatric patients would be useful to establish diagnostic and therapeutic guidelines., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)