Promising Findings from Smallpox Vaccine Trials Against Mpox

Recent studies have highlighted encouraging safety and efficacy outcomes from trials using a smallpox vaccine to combat mpox, a viral disease that has seen a resurgence in recent years. While the mpox virus has been endemic in certain African regions since the 1970s, a new variant has emerged, prompting global concerns and a pressing need for effective vaccination strategies.

The LC16m8 vaccine, derived from an attenuated strain of the vaccinia virus, was initially developed to protect against smallpox and received approval for use against monkeypox in 2022. Previous research has indicated its effectiveness in animal models, but comprehensive assessments were necessary to fully understand its immunogenicity and safety.

A new study, recently published in eBioMedicine, conducted by researchers from the University of Tokyo, has provided vital insights into the vaccine's performance across various species. The team led by Associate Professor Kouji Kobiyama evaluated the immune responses elicited by LC16m8 in different mouse strains, non-human primates, and human volunteers.

The researchers administered the vaccine to three strains of mice (BALB/c, C57BL/6J, and CAST/EiJ) and monitored their immune reactions and protection levels against mpox. In parallel, cynomolgus monkeys were vaccinated with a high dose of LC16m8 to assess safety parameters, including changes in weight, body temperature, and other local or systemic reactions.

The findings revealed that LC16m8 effectively stimulated robust immune responses in all tested mouse models, promoting critical immune cell types that are essential for sustained protection. Notably, CAST/EiJ mice exhibited reduced viral loads in lung tissue, underscoring the vaccine's protective capabilities.

In cynomolgus monkeys, the vaccine produced localized pox lesions without significantly impacting their overall health metrics, confirming its safety profile. In human trials, the vaccine successfully generated neutralizing antibodies against multiple strains of the mpox virus, with no serious adverse events reported during the follow-up period.

These results suggest that LC16m8 holds promise as a safe and effective option for mpox vaccination. The cross-species analysis utilized in this research could serve as a model for the development of future vaccines targeting not only poxviruses but also other emerging infectious diseases.

As the study indicates, accelerating the approval and deployment of LC16m8 in regions with high susceptibility to mpox outbreaks, particularly in Africa, could significantly lower transmission rates and alleviate the burden on healthcare systems. However, further investigations are necessary to optimize the vaccine's safety and efficacy, especially among naïve and immunocompromised individuals.

Ultimately, these findings contribute to establishing a more robust global response system for infectious diseases, enhancing preparedness for future health threats.