Yellow fever vaccination in Brazil: Short-term safety and immunogenicity in juvenile autoimmune rheumatic diseases

YF17D-based vaccines - standing on the shoulders of a giant

Live-attenuated yellow fever vaccine (YF17D) was developed in the 1930s as the first ever empirically derived human vaccine. Ninety years later, it is still a benchmark for vaccines made today. YF17D triggers a particularly broad and polyfunctional response engaging multiple arms of innate, humoral and cellular immunity. This unique immunogenicity translates into an extraordinary vaccine efficacy and outstanding longevity of protection, possibly by single-dose immunization. More recently, progress in molecular virology and synthetic biology allowed engineering of YF17D as a powerful vector and promising platform for the development of novel recombinant live vaccines, including two licensed vaccines against Japanese encephalitis and dengue, even in paediatric use. Likewise, numerous chimeric and transgenic preclinical candidates have been described. These include prophylactic vaccines against emerging viral infections (e.g. Lassa, Zika and SARS-CoV-2) and parasitic diseases (e.g. malaria), as well as therapeutic applications targeting persistent infections (e.g. HIV and chronic hepatitis), and cancer. Efforts to overcome historical safety concerns and manufacturing challenges are ongoing and pave the way for wider use of YF17D-based vaccines. In this review, we summarize recent insights regarding YF17D as vaccine platform, and how YF17D-based vaccines may complement as well as differentiate from other emerging modalities in response to unmet medical needs and for pandemic preparedness.

Yellow fever neutralizing antibody seroprevalence proportion and titers in previously vaccinated adults with chronic kidney disease

Studies on yellow fever vaccine (YF) in chronic kidney disease (CKD) patients are scarce. This cross-sectional study aimed to evaluate YF neutralizing antibody seroprevalence and titers in previously vaccinated adults with CKD, on dialysis (D-CKD) or not (ND-CKD), compared to healthy persons. The micro Plaque Reduction Neutralization-Horseradish Peroxidase (μPRN-HP) test was used. Antibody titers were expressed as the reciprocal of the highest dilution that neutralized the challenge virus by 50 % (μPRN50). Seropositivity cut-off was set at ≥ 1:100. We included 153 participants: 46 ND-CKD, 50 D-CKD and 57 healthy adults. Median ages were 58.3, 55 and 52.2 years, respectively. Median time since YF vaccination was 22.3, 18.5 and 48.3 months respectively. There were no statistically significant differences in YF seroprevalence and neutralizing antibodies titers among groups: 100 % of ND-CKD; 96 % of D-CKD and 100 % of healthy participants were seropositive. Geometric mean titers (GMT) were 818.5, 683.0 and 665.5, respectively (p = 0.289).

Yellow Fever Vaccine-Associated Viscerotropic Disease among Siblings, São Paulo State, Brazil

We describe 5 cases of yellow fever vaccine-associated viscerotropic disease (YEL-AVD) in 2 familial clusters during the 2017-2018 yellow fever (YF) vaccination campaign in São Paulo state, Brazil. The first case was that of a 40-year-old white man who died of icterohemorrhagic syndrome, which was confirmed to be YEL-AVD by using real-time reverse transcription PCR to detect 17DD YF vaccine in the liver. Ten years previously, his brother died of a clinically similar disease without a confirmed diagnosis 9 days after YF vaccination. The second cluster included 3 of 9 siblings in whom hepatitis developed in the first week after receiving fractionated doses of YF vaccine. Two of them died of hemorrhagic diathesis and renal and respiratory failure, and 17DD-YF vaccine was detected in serum samples from all patients and in the liver in 1 case. Genetic factors might play a substantial role in the incidence of YEL-AVD.

Vaccinology in pediatric rheumatology: Past, present and future

With the introduction of biological disease-modifying antirheumatic drugs (bDMARDs), the treatment of pediatric patients with autoimmune/inflammatory rheumatic diseases (pedAIIRD) has advanced from the "Stone Age" to modern times, resulting in much better clinical outcomes. However, everything comes with a price, and use of new bDMARDs has resulted in an increased risk of infections. Therefore, preventing infections in pedAIIRD patients is one of the top priorities. The most effective preventive measure against infection is vaccination. The first study on humoral immunity after vaccination in pediatric rheumatology was published in 1974 and on safety in 1993. For many years, data about safety and immunogenicity in pedAIIRD patients were available only for non-live vaccines and the first studies on live-attenuated vaccines in pedAIIRD patients treated with immunosuppressive therapy were available only after 2007. Even today the data are limited, especially for children treated with bDMARDs. Vaccinations with non-live vaccines are nowadays recommended, although their long-term immunogenicity and efficacy in pedAIIRD patients are still under investigation. Vaccinations with live-attenuated vaccines are not universally recommended in immunosuppressed patients. However, measles-mumps-rubella booster and varicella zoster virus vaccination can be considered under specific conditions. Additional research is needed to provide more evidence on safety and immunogenicity, especially regarding live-attenuated vaccines in immunosuppressed patients with pedAIIRD. Due to the limited number of these patients, well-designed, prospective, international studies are needed. Further challenges were presented by the COVID-19 pandemic. This mini review article reviews past and present data and discusses the future of vaccinology in pediatric rheumatology.