A Systematic Review and a Meta-Analysis of the Yellow Fever Vaccine in the Elderly Population

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 Vaccine-Related Neurotropic Disease in Brazil Following Immunization with 17DD

The disease burden of yellow fever virus infection (YFV) is quite high in the tropics where vaccination coverage is low. To date, vaccination is the most effective control strategy to mitigate and eliminate the burden of YF disease. The licensed YF vaccines are safe and effective and serious adverse events are rare. Herein, we report three cases of neurological syndrome, compatible with meningoencephalitis following 17DD vaccination. In all cases, YFV-specific IgM antibodies were detected in the cerebrospinal fluid. Our observations confirm the development of YF vaccine-associated neurotropic disease, a rare serious adverse event, from which all three patients have fully recovered without any long-term sequelae. This report reinforces the need for awareness among health professionals to recognize and effectively manage such events in a timely manner.

Mosquito Vectors (Diptera: Culicidae) and Mosquito-Borne Diseases in North Africa

Mosquitoes (Diptera: Culicidae) are of significant public health importance because of their ability to transmit major diseases to humans and animals, and are considered as the world's most deadly arthropods. In recent decades, climate change and globalization have promoted mosquito-borne diseases' (MBDs) geographic expansion to new areas, such as North African countries, where some of these MBDs were unusual or even unknown. In this review, we summarize the latest data on mosquito vector species distribution and MBDs affecting both human and animals in North Africa, in order to better understand the risks associated with the introduction of new invasive mosquito species such as Aedes albopictus. Currently, 26 mosquito species confirmed as pathogen vectors occur in North Africa, including Aedes (five species), Culex (eight species), Culiseta (one species) and Anopheles (12 species). These 26 species are involved in the circulation of seven MBDs in North Africa, including two parasitic infections (malaria and filariasis) and five viral infections (WNV, RVF, DENV, SINV and USUV). No bacterial diseases have been reported so far in this area. This review may guide research studies to fill the data gaps, as well as helping with developing effective vector surveillance and controlling strategies by concerned institutions in different involved countries, leading to cooperative and coordinate vector control measures.