Vaccination uptake has decreased globally in recent years, with a subsequent rise of vaccine-preventable diseases. Travellers, immunocompromised patients (ICP), and healthcare workers (HCW) are groups at increased risk for (severe) infectious diseases due to their behaviour, health, or occupation, respectively. While targeted vaccination guidelines are available, vaccination uptake seems low. In this review, we give a comprehensive overview of determinants—based on the integrated change model—predicting vaccination uptake in these groups. In travellers, low perceived risk of infection and low awareness of vaccination recommendations contributed to low uptake. Additionally, ICP were often unaware of the recommended vaccinations. A physician’s recommendation is strongly correlated with higher uptake. Furthermore, ICP appeared to be mainly concerned about the risks of vaccination and fear of deterioration of their underlying disease. For HCW, perceived risk of (the severity of) infection for themselves and for their patients together with perceived benefits of vaccination contribute most to their vaccination behaviour. As the determinants that affect uptake are numerous and diverse, we argue that future studies and interventions should be based on multifactorial health behaviour models, especially for travellers and ICP as only a limited number of such studies is available yet.

Certain "exotic" viruses are known to cause clinical diseases with potential liver involvement. These include viruses, beyond regular hepatotropic viruses (hepatitis A, -B(D), -C, -E, cytomegalovirus, Epstein-Barr virus), that can be found in (sub)tropical areas and can cause "exotic viral hepatitis". Transmission routes typically involve arthropods (Crimean Congo haemorrhagic fever, dengue, Rift Valley fever, yellow fever). However, some of these viruses are transmitted by the aerosolised excreta of rodents (Hantavirus, Lassa fever), or via direct contact or contact with bodily fluids (Ebola). Although some exotic viruses are associated with high fatality rates, such as Ebola for example, the clinical presentation of most exotic viruses can range from mild flu-like symptoms, in most cases, right through to being potentially fatal. A smaller percentage of people develop severe disease with haemorrhagic fever, possibly with (fulminant) hepatitis. Liver involvement is often caused by direct tropism for hepatocytes and Kupffer cells, resulting in virus-mediated and/or immune-mediated necrosis. In all exotic hepatitis viruses, PCR is the most sensitive diagnostic method. The determination of IgM/IgG antibodies is a reasonable alternative, but cross-reactivity can be a problem in the case of flaviviruses. Licenced vaccines are available for yellow fever and Ebola, and they are currently under development for dengue. Therapy for exotic viral hepatitis is predominantly supportive. To ensure that preventive measures can be introduced to control possible outbreaks, the timely detection of these viruses is very important.

Purpose: Patients with inborn errors of immunity (IEI) are at increased risk of severe coronavirus disease-2019 (COVID-19). Effective long-term protection against COVID-19 is therefore of great importance in these patients, but little is known about the decay of the immune response after primary vaccination. We studied the immune responses 6 months after two mRNA-1273 COVID-19 vaccines in 473 IEI patients and subsequently the response to a third mRNA COVID-19 vaccine in 50 patients with common variable immunodeficiency (CVID). Methods: In a prospective multicenter study, 473 IEI patients (including X-linked agammaglobulinemia (XLA) (N = 18), combined immunodeficiency (CID) (N = 22), CVID (N = 203), isolated or undefined antibody deficiencies (N = 204), and phagocyte defects (N = 16)), and 179 controls were included and followed up to 6 months after two doses of the mRNA-1273 COVID-19 vaccine. Additionally, samples were collected from 50 CVID patients who received a third vaccine 6 months after primary vaccination through the national vaccination program. SARS-CoV-2-specific IgG titers, neutralizing antibodies, and T cell responses were assessed. Results: At 6 months after vaccination, the geometric mean antibody titers (GMT) declined in both IEI patients and healthy controls, when compared to GMT 28 days after vaccination. The trajectory of this decline did not differ between controls and most IEI cohorts; however, antibody titers in CID, CVID, and isolated antibody deficiency patients more often dropped to below the responder cut-off compared to controls. Specific T cell responses were still detectable in 77% of controls and 68% of IEI patients at 6 months post vaccination. A third mRNA vaccine resulted in an antibody response in only two out of 30 CVID patients that did not seroconvert after two mRNA vaccines. Conclusion: A similar decline in IgG titers and T cell responses was observed in patients with IEI when compared to healthy controls 6 months after mRNA-1273 COVID-19 vaccination. The limited beneficial benefit of a third mRNA COVID-19 vaccine in previous non-responder CVID patients implicates that other protective strategies are needed for these vulnerable patients.

In response to the mpox outbreak in 2022 and 2023, widespread vaccination with modified vaccinia Ankara-Bavarian Nordic (MVA-BN, also known as JYNNEOS or Imvanex) was initiated. Here, we demonstrate that orthopoxvirus-specific binding and MVA-neutralising antibodies waned to undetectable levels 1 year post vaccination in at-risk individuals who received two doses of MVA-BN administered subcutaneously with an interval of 4 weeks, without prior smallpox or mpox vaccination. Continuous surveillance is essential to understand the impact of declining antibody levels.

Bacterial bloodstream infections (BSIs) are a serious complication after hematopoietic stem cell transplantation (HSCT), especially when caused by multidrug-resistant (MDR) bacteria. However, data on BSIs post-HSCT from centers in sub-Saharan Africa are limited. This study aims to describe the incidence, etiology, and outcomes of BSIs, including those caused by Carbapenem-Resistant Enterobacterales (CRE), in both autologous and allogenic HSCT recipients in South Africa. Furthermore, this study examines the incidence and clinical impact of colonization with CRE. A retrospective analysis was performed on clinical data from HSCT recipients, transplanted between January 2018 and December 2023 at Groote Schuur Hospital (GSH) and Red Cross War Memorial Children's Hospital (RCWMCH), the academic hospitals of the University of Cape Town. Data were extracted from the transplant unit electronic and paper patient records, Hematology Patient Registry, and the National Health Laboratory Service electronic database. Surveillance cultures were taken upon admission and subsequently repeated weekly for GSH patients. In total, 270 HSCT recipients were included: 145 underwent autologous HSCT and 124 an allogenic HSCT. The most common indication for autologous HSCT was multiple myeloma (52%), while acute myeloid leukemia (AML) was the most frequent for allogenic HSCT (34%). The overall incidence of BSIs was 35%, with a higher rate observed in allogeneic HSCT recipients (48%) compared to autologous HSCT recipients (23%). Gram-negative bacteria (GNB) were the most common pathogens, and CRE were responsible for 9% of BSIs. Carbapenem-resistant Klebsiella pneumonia spp was the most common CRE found in BSI and rectal surveillance cultures. Surveillance cultures with CRE were detected in 19% of the HSCT recipients during admission to the transplant unit, with OXA-48 (and variants) the most prevalent carbapenemase. Colonization by CRE was an independent risk factor for developing BSIs. Within 100 days post-HSCT, 25 HSCT recipients (9%) died, of whom nine (36%) had a BSI in the last seven days of life. Bivariate analysis revealed that BSIs significantly reduced overall survival in both autologous and allogenic HSCT recipients, with a further decrease in survival when the BSI was caused by MDR bacteria. BSIs are a frequent and severe complication among HSCT recipients in South Africa, particularly in those receiving allogenic HSCT. Colonization with CRE significantly increases the risk of BSIs, underscoring the need for vigilant infection control and targeted antimicrobial strategies in this vulnerable population.

Healthcare workers (HCW) are at increased risk of contracting hepatitis B virus (HBV) and are, therefore, vaccinated pre-exposure. In this study, the HBV vaccination programme for medical students in a university hospital in the Netherlands was evaluated. In the first part, the effectiveness of the programme, which consisted of a vaccination with Engerix-B^® at 0, 1, and 6 months, was retrospectively evaluated over 7 years (2012–2019). In the second part of this study, we followed students (the 2019 cohort) who had previously been vaccinated against HBV vaccination (4–262 months prior to primary presentation) in order to investigate the most efficient strategy to obtain an adequate anti hepatitis B surface antigen titre. In the latter, titre determination was performed directly during primary presentation instead of giving previously vaccinated students a booster vaccination first. The vaccination programme, as evaluated in the retrospective first part of the study, was effective (surpassed the protection limit of 10 IU/L) in 98.8 percent of the students (95% CI (98.4–99.2)). In the second part of our study, we found that 80 percent (95% CI (70–87)) of the students who had previously been vaccinated against HBV were still sufficiently protected and did not require a booster vaccination. With this strategy, the previously vaccinated students needed an average of 1.4 appointments instead of the 2 appointments needed with the former strategy. This knowledge is important and can save time and resources in the process of occupational HBV vaccination of HCW.