17D yellow fever vaccine elicits comparable long-term immune responses in healthy individuals and immune-compromised patients.

BACKGROUND: The 17D live attenuated yellow fever (YF) vaccine is contra-indicated in immune-compromised individuals and may elicit a suboptimal immunologic response. The aim of this study is to assess whether long-term immune responses against the YF vaccine are impaired in immune-compromised patients. MATERIALS AND METHODS: Fifteen patients using different immunosuppressive drugs and 30 healthy individuals vaccinated 0-22 years ago were included. The serological response was measured using the plaque reduction neutralization test (PRNT). CD8(+) and CD4(+) T-cell responses were measured following proliferation and re-stimulation with YFV peptide pools. Phenotypic characteristics and cytokine responses of CD8(+) T-cells were determined using class I tetramers. RESULTS: The geometric mean titre of neutralizing antibodies was not different between the groups (p = 0.77). The presence of YFV-specific CD4(+) and CD8(+) T-cell did not differ between patients and healthy individuals (15/15, 100.0% vs. 29/30, 96.7%, p = 0.475). Time since vaccination correlated negatively with the number of YFV-specific CD8(+) T-cells (r = -0.66, p = 0.0045). Percentages of early-differentiated memory cells increased (r = 0.67, p = 0.017) over time. CONCLUSION: These results imply that YF vaccination is effective despite certain immunosuppressive drug regimens. An early-differentiated memory-like phenotype persisted, which is associated with effective expansion upon re-encounter with antigen, suggesting a potent memory T-cell pool remains.

Risk of rabies exposure among travellers.

BACKGROUND: In recent years, requests for rabies immunoglobulin have increased at Amsterdam's Academic Medical Center's travel clinic. Travellers who received rabies pre-exposure prophylaxis (PrEP) before travel departure have immunological memory that can quickly be activated by timely booster vaccinations after possible exposure to rabies. PrEP alleviates the need for costly and scarcely available rabies immunoglobulin in case of exposure. This study describes which travellers are at risk of rabies exposure and would benefit from PrEP. The secondary aim was to specify which factors influence decision-making on taking PrEP. METHODS: We reviewed electronic patient files of travellers attending our clinic for rabies post-exposure prophylaxis between January 2009 and February 2014. Demographic and travel characteristics were compared with a sample of patients who were seen for pre-travel advice at our clinic. To assess which factors had influenced the decision to take PrEP, a questionnaire survey was conducted. RESULTS: A total of 161 travellers experienced animal-associated injury. Compared with travellers from the pre-travel database, more people travelled to Southeast Asia (49.5% vs. 30.9%, p = 0.035) for comparable time periods (median 21 vs. 21 days, p = 0.083). Transcutaneous injuries (type III) were common (73.9%), most often inflicted by dogs (45%). Only ten travellers (6.2%) had received PrEP. Barriers for PrEP were high costs and a short time interval between consultation and travel departure. CONCLUSION: Travellers t o Southeast Asia should particularly be informed about rabies and the possibility of PrEP. Long-term travel was not associated with a higher risk of rabies exposure.

Rabies vaccinations: are abbreviated intradermal schedules the future?

Rabies is a deadly disease, and current preexposure vaccination schedules are lengthy and expensive. We identified nine studies investigating abbreviated schedules. Although initial responses were lower, accelerated adequate immune responses were elicited after booster vaccinations. Lower-dose (and therefore cheaper) vaccination schedules may constitute a valid alternative to current vaccination schedules.