Agranulocytosis following injection of inactivated Japanese encephalitis vaccine (Vero cell): A case report.

BACKGROUND: Japanese encephalitis virus (JEV), a mosquito borne flavivirus, is the leading cause of viral encephalitis in Asia, in terms of frequency and severity. JEV infection is thought to confer lifelong immunity. With the near eradication of poliomyelitis, JEV is now the continent's leading cause of childhood viral neurologic infection and disability. The most common clinical manifestation of JEV infection is acute encephalitis, and currently there is no specific antiviral therapy. Japanese Encephalitis Vaccine (JE-VC) is an effective prevention measure, including JE-VC, Live (JE-MB), and Inactivated JE-VC.

CASE SUMMARY: A 9-mo-old girl received injection of Inactivated JE-VC (Vero cell) (Liaoning Chengda, batch number 201611B17) on August 31, 2017. On that night, she developed a fever with the body temperature up to 38.5 °C, for which Ibuprofen Suspension Drops 1.25 mL was given as antipyretic treatment. On September 1, the patient developed apocleisis, and her parents noticed herpes in her oral cavity. The patient was sent to our hospital on September 3. Physical examination led to a diagnosis of herpetic stomatitis, for which Stomatitis Spray 1 puff, tid, Kangfuxin Liquid 2 mL, tid, and vitamin B2 0.5 tablet, tid, were prescribed. Routine blood tests for low fever on September 6, 2017 revealed an absolute neutrophil count (ANC) of 0.62 × 109 /L, hemoglobin (Hb) of 109 g/L, and platelet count (PLT) of 308 × 1012 /L, and the tests were monitored regularly thereafter. The patient was followed until July 26, 2020, when routine blood tests revealed ANC 1.72 × 109 /L, Hb 138 g/L, and PLT 309 × 1012 /L, indicating that the neutropenia count had normalized.

CONCLUSION: This report attempts to bring to clinical attention that Inactivated JE-VC (Vero cell) might cause prolonged granulocytopenia or even agranulocytosis.