Immune Response during Adverse Events after 17D‐Derived Yellow Fever Vaccination in Europe

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Abstract
Background. In 1999–2000, reports of fatalities after vaccination with 17D-derived yellow fever vaccine (YEL) focused mainly on cases of YEL-associated adverse events (YEL-AEs) and YEL-associated viscerotropic disease (YEL-AVD). Here, we investigated 6 recent European cases to provide insight regarding immune response involvement and to identify potential risk factors. Methods. Clinical, microbiological, molecular biological, and immunological assays were performed on serum from 6 patients with YEL-AEs, including 5 with YEL-AVD and 1 with YEL-associated neurotropic disease (YEL-AND). Results. The levels of 3 liver enzymes associated with infection were clearly increased in all patients with YEL-AVD, but no elevations were observed in the patient with YEL-AND. In the patients with severe YEL-AVD, platelet counts were markedly reduced (Conclusions. Onthe basis of these results, we conclude that elevations in cytokine levels and reductions in platelet counts are suitable surrogate markers for patients likely to experience severe adverse reactions to YEL.