LAUSR

Background Hematopoietic cell transplantation (HCT) recipients are increased risk for vaccine-preventable infections (VPI). However, the true prevalence of VPI in children post-HCT is unknown. Methods We performed an epidemiological study using the Pediatric Health Information System (PHIS) database in children and young adults who underwent allogeneic (allo) and autologous (auto) HCT and had a first hospitalization with a VPI (as defined by ICD-9 and ICD-10 codes) within 5-yr post-HCT between Jan 1, 2010 and Dec 31, 2018 at the 45 participating US PHIS hospitals. Prevalence for overall VPI and by infection were calculated at the following timepoints: at initial HCT admission, HCT discharge to D100, D101-D180, 6-12 months, 1-2 yr, and 2-5 yr post-HCT. Results We identified 9,591 unique HCT recipients (alloHCT: 6,602, 69%; autoHCT: 2,989, 31%) with a median age of 6.7 years (range infant-18.9 yrs) during the 8-yr study period. Of these, 684 HCT recipients (510 alloHCT, 174 autoHCT) were hospitalized with VPI in the first 5 yrs after HCT, for an overall prevalence of 7.1%. VPI occurred more frequently among alloHCT (8%) than autoHCT recipients (6%) at all time-points (p=0.0008). VPI hospitalizations occurred a median of 221 days post-HCT [range 0-5 yrs] with the majority occurring in the first 6-12 mos post-HCT (Figure 1). Influenza was the most frequent VPI (4.05%) (Table I). Conclusion The overall prevalence of VPI hospitalizations after pediatric HCT was 7.1%, occurring most frequently in the first 6-12 months post HCT and among alloHCT recipients. Continued efforts to prevent VPI, including optimizing vaccination strategies in this population, are warranted.