Publications by authors named "Leo G Visser"

Article Synopsis
  • This study investigates the occurrence, symptom patterns, and factors influencing post-acute COVID symptoms in a sample of the Dutch population using data from the COVID RADAR app.
  • The research included 1478 participants who recorded their symptoms from 40 days before to 100 days after a positive COVID test, identifying cough, loss of smell or taste, and fatigue as the most common ongoing symptoms.
  • The findings revealed that about 8% of participants still had symptoms after 100 days, with symptoms grouped into three clusters and vaccination linked to a reduced risk of long-term symptoms, highlighting the complexity of post-acute COVID experiences.
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  • The study aimed to analyze how the body processes trimethoprim, sulfamethoxazole, and its metabolite N-acetyl sulfamethoxazole in hospitalized patients, especially in relation to dosing for infections like Pneumocystis jirovecii pneumonia.
  • It utilized data from 168 patients and established two pharmacokinetic models to optimize dosing regimens, taking into account factors like kidney function (eGFR) and continuous renal replacement therapy (CRRT).
  • Findings indicated that standard dosing was sufficient for patients with normal kidney function, but those with reduced kidney function needed lower doses, and CRRT patients required higher doses of sulfamethoxazole for effective treatment.
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Bivalent COVID-19 vaccines comprising ancestral Wuhan-Hu-1 (WH1) and the Omicron BA.1 or BA.5 subvariant elicit enhanced serum antibody responses to emerging Omicron subvariants.

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Background: Electronic informed consent (eConsent) usage has expanded in recent years in Europe, especially during the pandemic. Slow recruitment rate and limitations in participant outreach are the challenges often faced in clinical research. Given the benefits of eConsent and group counselling reported in the literature, group eConsent was implemented in recruitment for the SWITCH-ON study.

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Article Synopsis
  • Travellers to rabies-endemic countries often lack adequate knowledge about the virus and risk prevention, with over 21% having poor understanding.
  • A study involving Dutch travellers showed significant gaps in knowledge about transmission (like cats and bats) and post-exposure prophylaxis (PEP) requirements.
  • To improve safety, there is a call for enhanced pre-travel education focusing on avoiding animal contact and understanding when to seek PEP after potential exposure.
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Suspected allergic reactions after mRNA COVID-19 vaccination withheld multiple individuals from getting fully vaccinated during the pandemic. We vaccinated adults who had experienced possible allergic symptoms after their first intramuscular dose of a COVID-19 mRNA vaccine with a 1/5th fractional intradermal test dose of the mRNA-1273 (Moderna) COVID-19 vaccine. No anaphylactic reactions were observed after intradermal vaccination (n = 56).

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Background: Fractional-dosed intradermal (i.d.) vaccination produces antibody concentrations above the proposed proxy for protection against severe disease as compared with intramuscular (i.

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Article Synopsis
  • Antibody responses from COVID-19 vaccinations are decreasing, especially with the rise of the Omicron variant, prompting the need for new bivalent mRNA booster vaccines containing both ancestral and Omicron spike proteins.
  • A study evaluated how different initial vaccination regimens (priming) influenced the effectiveness of these bivalent boosters, revealing that while the boosters increased neutralizing antibodies and T-cell responses, they were less effective against the newer XBB.1.5 variant.
  • The findings support using vaccines tailored to current circulating strains for vulnerable populations and stress the need for ongoing monitoring of immune responses to inform future vaccination strategies.
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Objectives: The aim of this study was to assess the safety and immunogenicity of a dose-sparing fractional intradermal (ID) booster strategy with the mRNA-1273 COVID-19 vaccine.

Methods: COVID-19 naive adults aged 18-30 years were recruited from a previous study on primary vaccination regimens that compared 20 μg ID vaccinations with 100 μg intramuscular (IM) vaccinations with mRNA-1273 as the primary vaccination series. Participants previously immunized with ID regimens were randomly assigned (1:1) to receive a fractional ID booster dose (20 μg) or the standard-of-care intramuscular (IM) booster dose (50 μg) of the mRNA-1273 vaccine, 6 months after completing their primary series (ID-ID and ID-IM group, respectively).

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The absence of a consensus-based reference standard for urinary tract infection (UTI) research adversely affects the internal and external validity of diagnostic and therapeutic studies. This omission hinders the accumulation of evidence for a disease that imposes a substantial burden on patients and society, particularly in an era of increasing antimicrobial resistance. We did a three-round Delphi study involving an international, multidisciplinary panel of UTI experts (n=46) and achieved a high degree of consensus (94%) on the final reference standard.

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Fractional dosing can be a cost-effective vaccination strategy to accelerate individual and herd immunity in a pandemic. We assessed the immunogenicity and safety of primary intradermal (ID) vaccination, with a 1/5th dose compared with the standard intramuscular (IM) dose of mRNA-1273 in SARS-CoV-2 naïve persons. We conducted an open-label, non-inferiority, randomized controlled trial in the Netherlands between June and December 2021.

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Introduction: Immunocompromised kidney patients are at increased risk of prolonged SARS-CoV-2 infection and related complications. Preclinical evidence demonstrates a more potent inhibitory effect of voclosporin on SARS-CoV-2 replication than tacrolimus . We investigated the potential antiviral effects of voclosporin on SARS-CoV-2 in immunocompromised patients.

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Background: Vaccine development against hookworm is hampered by the absence of the development of protective immunity in populations repeatedly exposed to hookworm, limiting identification of mechanisms of protective immunity and new vaccine targets. Immunisation with attenuated larvae has proven effective in dogs and partial immunity has been achieved using an irradiated larvae model in healthy volunteers. We aimed to investigate the protective efficacy of immunisation with short-term larval infection against hookworm challenge.

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Article Synopsis
  • Urinary tract infections (UTIs) are common but difficult to diagnose in older women due to complications like cognitive impairment and the presence of asymptomatic bacteria.
  • This study assessed the accuracy of 12 urine biomarkers in diagnosing UTIs among women aged 65 and older who displayed specific symptoms.
  • Five biomarkers showed strong discriminative ability for diagnosing UTIs, with azurocidin having the highest accuracy; combining biomarkers with standard tests improved diagnostic capability compared to using pyuria alone.
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Background: After rabies pre-exposure prophylaxis (PrEP) vaccination, scarcely available rabies immunoglobulins are not required for post-exposure prophylaxis (PEP). However, PrEP is not sufficiently accessible as it is cost-intensive and time-intensive. This study investigates whether rabies PrEP schedules can be shortened to one visit, removing some of these barriers.

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Introduction: Remdesivir is a registered treatment for hospitalised patients with COVID-19 that has moderate clinical effectiveness. Anecdotally, some patients' respiratory insufficiency seemed to recover particularly rapidly after initiation of remdesivir. In this study, we investigated if this rapid improvement was caused by remdesivir, and which patient characteristics might predict a rapid clinical improvement in response to remdesivir.

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Background: Prompt administration of post-exposure prophylaxis (PEP) is crucial to prevent a fatal rabies infection after an animal associated injury (AAI), preferably within 24 h. PEP, especially in case of a type III injury for which rabies immune globulin (RIG) is needed, is difficult to obtain abroad. This, along with the fear of potentially having contracted a lethal disease, might be an important source for anxiety and distress.

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Introduction: Nanoporous microneedle arrays (npMNA) are being developed as skin patches for vaccine delivery. As alternative for needle-based immunisation, they may potentially result in higher vaccine acceptance, which is important for future mass vaccination campaigns to control outbreaks, such as COVID-19, and for public vaccination in general. In this study we investigated the safety and immunogenicity of needle-free intradermal delivery of a fractional third or fourth dose of mRNA-1273 vaccine by npMNA.

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Defining urinary tract infection (UTI) is complex, as numerous clinical and diagnostic parameters are involved. In this systematic review, we aimed to gain insight into how UTI is defined across current studies. We included 47 studies, published between January 2019 and May 2022, investigating therapeutic or prophylactic interventions in adult patients with UTI.

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Introduction: In 2020, the first Dutch West Nile virus (WNV) infected birds were detected through risk-targeted surveillance of songbirds. Retrospective testing of patients with unexplained neurological disease revealed human WNV infections in July and August 2020. Bird ringers are highly exposed to mosquito bites and possibly avian excrements during ringing activities.

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Objectives: The association of biological female sex with outcome in patients with Staphylococcus aureus bacteraemia remains unresolved. The aim of this study was to determine the independent association of female sex with management and mortality in patients with S. aureus bacteraemia.

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Background: Despite being the leading cause of mortality from bloodstream infections worldwide, little is known about regional variation in treatment practices for Staphylococcus aureus bacteremia (SAB). The aim of this study was to identify global variation in management, diagnostics, and definitions of SAB.

Methods: During a 20-day period in 2022, physicians throughout the world were surveyed on SAB treatment practices.

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