Vaccination responses and lymphocyte subsets after autologous stem cell transplantation

Twenty autologous stem cell transplant recipients were vaccinated with three doses of Diphtheria–Tetanus–Poliomyelitis vaccine and conjugated Haemophilus influenzae type b (Hib) vaccine. Pneumococcal vaccination consisted of two doses of conjugated vaccine followed by a single dose of polysaccharide vaccine, at 6, 8 and 14 months after transplantation, respectively. Mean anti-tetanus, anti-Hib and anti-pneumococcal IgG antibodies significantly increased after each vaccination. Response rates after the full vaccination schedule were 94%, 78% and 61% for Hib, conjugated 7-valent pneumococcal vaccine and non-conjugated 23-valent pneumococcal vaccine, respectively. Three months after transplantation, CD16+CD56+ NK cells were in the normal range and remained so. The total number of T lymphocytes at 3 months was and remained in the normal range. The mean CD4/CD8 ratio was 0.43 at 3 months post aSCT and, while gradually increasing, remained subnormal. The mean number of CD19+ B lymphocytes significantly increased during the study period. Patients with CD19 counts <0.10 × 109 L−1 required at least two Hib vaccinations to show a response, while the majority of patients with CD19 counts ≥0.20 × 109 L−1 showed a response to Hib after one vaccination only. Thus, a minimum threshold level of CD19+ cells appears to be required for adequate responses to vaccination.