Compliance with yellow fever and measles vaccines in the revaccination program post-hematopoietic cell transplantation.

INTRODUCTION: Measles, mumps, rubella, and even poliomyelitis outbreaks have recently perplexed infectious disease clinicians and epidemiologists globally due to the decline in vaccination coverage rates in children and adults. Measles and yellow fever (YF) have represented an increasing burden on the Brazilian public health system in recent decades. Both diseases are preventable by live-attenuated viral vaccines (LAVV), which have restricted use in hematopoietic cell transplant (HCT) recipients. METHODS: Autologous and allogeneic HCT recipients returning for regular appointments at the outpatient clinic were invited to participate in the study. Patients transplanted for at least 2 years and with a printed copy of the vaccination record were included. RESULTS: We assessed the vaccination records of 273 HCT recipients after the second year of HCT (193 allogeneic and 80 autologous) and observed lower compliance with the YF vaccine (58 patients, 21.2%) than with the measles vaccine (138 patients, 50.5%, p ≤ .0001). This is the largest published series of YF vaccination in HCT recipients so far. No severe adverse events occurred. Although expected, chronic graft-versus-host disease (GVHD) did not affect the compliance with measles (p = .08) or YF vaccination (p = .7). Indeed, more allogeneic recipients received measles vaccine in comparison with autologous patients (p < .0001), suggesting that chronic GVHD was not the main reason for not being vaccinated. Children and allogeneic HCT were more likely to receive measles vaccine. Time elapsed from HCT >5 years favored both measles and YF vaccination. CONCLUSION: A better understanding of the reasons for low compliance with LAVV is necessary to overcome this problem.

Poor response to hepatitis A vaccination in hematopoietic stem cell transplant recipients.

BACKGROUND: Hepatitis A virus (HAV) infection is highly prevalent in developing countries. In countries experiencing a shift from intermediate/high endemicity to low endemicity, the World Health Organization recommends the incorporation of HAV vaccine into the national vaccination calendar for children aged ≥1 year. Since HAV antibodies wane over time, most HSCT revaccination guidelines advise vaccination as optional, following the country recommendation. However, no study has evaluated the serological response to HAV vaccine in allogeneic HSCT recipients. METHODS: We conducted a prospective study in 46 HSCT recipients who received two doses of inactivated HAV vaccine. Blood samples were taken before vaccination to determine HAV prevalence rates, and before and 4-6 weeks after the second dose. Specific anti-HAV antibodies were detected by a competitive commercial enzyme immune assay. RESULTS: Patients received the first dose of vaccine at a median of 332.5 (120-4134) days after HSCT. Median absolute lymphocyte count at vaccination was 1947 (696-12 500)/mm3 . The seroprevalence rate was 93.5% at inclusion. Although safe and well tolerated, the serological response to HAV vaccine in susceptible patients was poor (33%), and no boost effect was observed in seropositive patients. CONCLUSIONS: In areas with intermediate/high seroprevalence of HAV, serology should be recommended prior to referral to vaccination. The mechanisms of antibody interference and how to overcome T-cell function deficiency need to be better understood in transplant populations receiving HAV vaccine. Alternative schedules of HAV vaccination should be evaluated in prospective trials.

Latent and active tuberculosis infection in allogeneic hematopoietic stem cell transplant recipients: a prospective cohort study.

Tuberculosis (TB) is a major infectious complication in hematopoietic stem cell transplant (HSCT) recipients in countries with high TB prevalence. Identifying and treating latent tuberculosis infection (LTBI) helps to prevent TB reactivation after transplantation. Few studies have compared the tuberculin skin test (TST) with interferon Gamma release assays (IGRA) to diagnose LTBI in HSCT candidates. We compared TST and QuantiFeron TB gold in tube (QTF-GIT) and prospectively evaluated the incidence of active tuberculosis in 126 HSCT candidates and 58 HSCT recipients with chronic GVHD followed at the outpatient clinic. TB was diagnosed by culture in Mycobacteria media and by commercial real-time PCR kit. Considering the positivity of any test, the prevalence of LTBI was 8.7% in HSCT candidates (11 out of 126) and 12.5% in HSCT recipients with chronic GVHD (6 out of 48). QTF-GIT indeterminate results were detected in 2.4% of the HSCT candidates. Fair to good agreement (K > 0.50) between tests was observed in both cohorts. Cumulative incidence of TB was 3% in the GVHD cohort. TB was diagnosed in 2 chronic GVHD recipients, both cases confirmed by positive culture and PCR. None of the 11 patients with LTBI diagnosed pre-HSCT who received INH prophylaxis developed TB.

Thymopoiesis in Pre- and Post-Hematopoietic Stem Cell Transplantation.

Hematopoietic stem cell transplantation (HSCT) is an important therapeutic option for some hematological diseases. However, patients who undergo HSCT acquire a state of immunodeficiency that causes significant mortality. Reconstitution of thymic function is needed to support the immune system. One way to measure thymic function is through T-cell receptor excision circle (TREC) quantification. TRECs are generated by T-cell receptor gene rearrangements during T-cell maturation in the thymus and represent a reliable marker for thymic output. In this study, we aimed to assess aging and malignant hematological diseases as two important factors that may influence thymic output before HSCT. We observed that patients before HSCT presented signal joint TREC (sjTREC) numbers lower than 606.55 copies/µg DNA (low values) compared with healthy individuals, with an odds ratio (OR) of 12.88 [95% confidence interval (CI): 5.26-31.53; p < 0.001]. Our results showed that a group of older individuals (≥50 years old), comprising both healthy individuals and patients, had an OR of 10.07 (95% CI: 2.80-36.20) for low sjTREC values compared with younger individuals (≤24 years old; p < 0.001). Multiple logistic regression analysis confirmed that both older age (≥50 years old) and malignant hematological diseases and their treatments were important and independent risk factors related to thymic function impairment (p < 0.001). The median sjTREC value for patients of all ages was significantly lower than the sjTREC median for the subgroup of older healthy individuals (≥50 years old; p < 0.001). These data suggested that patients before HSCT and healthy individuals exhibited age-dependent thymic impairment, and that prior treatment for hematological diseases may exacerbate aging-related deterioration of natural thymic function. Furthermore, we analyzed these patients 9 months post-HSCT and compared patients who underwent autologous HSCT with those who underwent allogeneic HSCT. Both groups of patients achieved sjTREC copy numbers similar to those of healthy individuals. We did not find a close relationship between impaired thymic function prior to HSCT and worse thymic recovery after HSCT.