This analysis indicates that VZV vaccination is feasible and justified in seronegative children with ALL, in countries where VZV vaccination is not part of the national vaccination program.

Introduction Chickenpox is caused by varicella zoster virus (VZV). Although predominantly a mild disease, it can cause considerable morbidity and in rare occasions even mortality in healthy children as well as increased morbidity and mortality in immunocompromised patients. The aetiology of appendicitis is largely unknown but is thought to be multifactorial. Appendicitis is a suspected, but not well documented, complication from varicella zoster virus infection. Case Presentation A five-year-old girl diagnosed with DiGeorge syndrome and a prolonged primary VZV infection was admitted due to abdominal pain, increasing diarrhoea, vomiting, and poor general condition. She developed perforated appendicitis and an intraperitoneal abscess. VZV DNA was detected by PCR in two samples from the appendix and pus from the abdomen, respectively. The child was treated with acyclovir and antibiotics and the abscess was drained twice. She was discharged two weeks after referral with no sequela. Conclusion Abdominal pain in children with viral infections can be a challenge, and appendicitis has to be considered as a complication to acute viral diseases, especially if the child is immunocompromised.

Improved methods are needed for diagnosing infectious diseases in children with cancer. Most children have fever for other reasons than bacterial infection and are exposed to unnecessary antibiotics and hospital admission. Recent research has shown that host whole blood RNA transcriptomic signatures can distinguish bacterial infection from other causes of fever. Implementation of this method in clinics could change the diagnostic approach for children with cancer and suspected infection. However, extracting sufficient mRNA to perform transcriptome profiling by standard methods is challenging due to the patient’s low white blood cell (WBC) counts. In this prospective cohort study, we succeeded in sequencing 95% of samples from children with leukaemia and suspected infection by using a low-input protocol. This could be a solution to the issue of obtaining sufficient RNA for sequencing from patients with low white blood cell counts. Further studies are required to determine whether the captured immune gene signatures are clinically valid and thus useful to clinicians as a diagnostic tool for patients with cancer and suspected infection.