T3. Studies of the epidemiology of infections in transplant patients and patients with impaired immunity due to underlying disease or immunosuppressive drugs
Background : Allo-HCT recipients are at increased risk for vaccine-preventable infections. Early vaccination (EV) beginning at 3-6 months (mo) post-HCT has been shown to be safe, immunogenic, and is recommended. We assessed adherence and immunogenicity to EV in children post allo-HCT.
Methods : Retrospective analysis of allo-HCT performed 1/1/10 - 6/30/18 at NCH. Children who died, relapsed, or received anti-CD20 biologics in the 6 mo preceding intended vaccination were excluded. Institutional guidelines recommend EV starting at 6 (+1) mo post-HCT with: 3 PCV13 +1 PPSV23, IPV, HBV, DTaP and HIB. Vaccination rates were analyzed at 6(+1), 8(+1) and 10(+1) mo post-HCT and serologies were obtained pre- and ≥ 4 weeks post vaccination. Immunogenicity was defined as antibody (Ab) concentrations ≥ 1.3 µg/mL or a 4 fold rise ≥ 70% of ten PCV13 serotypes, tetanus (T) and diphtheria (D) Ab ≥ 0.1 IU/mL, and HBs Ab ≥ 10 IU/ml. Non-parametric statistics were applied; correlations between T&B cell subsets and IgG pre-vaccination and specific Ab post-vaccination were performed.
Results : During the 8-year study period, 171 allo-HCT were performed: 131 children were eligible for EV (Table 1) however, EV occurred in only 49.6% (65/131) and was completed in 37.5% (45/120) of children at 10(+1) mo post-HCT.
Vaccine immunogenicity of PCV13, HBV, T & D was achieved in 40/45, 34/36, 63/64, and 18/18 of evaluable children, respectively. Protective Ab response after EV for PCV13, HBV, T & D was found in 21/24 (87.5%), 14/16 (87.5%), 35/36 (97.2%), and 8/8 (100%) children, respectively. Specific IgG geometric mean concentration pre- and post- vaccination were similar in children whether they received early or delayed vaccination (median 9.8 mo post-HCT, IQR 8-14) (Fig 1-2). No correlations were found between absolute CD4, CD8, CD19 and IgG pre-vaccination and vaccines specific Abs post-vaccination (Fig 3).
Conclusion : Despite recommendations, adherence to EV was low among our cohort of allo-HCT recipients and identified opportunities for improvement. Overall, vaccines were immunogenic with no significant differences in Ab concentrations among patients receiving early vs delayed vaccination. No robust correlations were found between number of T&B cells or total IgG and Ab titers.