WASHINGTON: An experimental Moderna mRNA vaccine for mpox has demonstrated greater effectiveness than current shots in reducing the viral disease symptoms and duration, according to an animal study published in the journal Cell on Wednesday.
The vaccine, which leverages the same mRNA technology used in Moderna’s widely successful COVID-19 vaccine, outperformed existing vaccines in terms of both safety and efficacy in animal models.
The study comes at a critical time as an outbreak of mpox in Africa, fueled in part by a new variant from the Democratic Republic of Congo, has been declared an international public health emergency.
Dr. Jay Hooper, a senior author and virologist at the US Army Medical Research Institute for Infectious Diseases, emphasized the goal of exploring mRNA technology to strike a “sweet spot” for mpox vaccines that maximizes safety and effectiveness.
Unlike current vaccines that were originally developed for smallpox and have limitations, Moderna’s mRNA vaccine introduces genetic instructions to help the immune system recognize and combat the virus more effectively.
Currently licensed vaccines for mpox, such as the JYNNEOS vaccine, utilize a “live attenuated” virus approach. This method involves using a weakened virus that cannot cause disease but also limits the vaccine’s protective efficacy. Another older vaccine, ACAM2000, has higher efficacy but comes with the risk of potential infection.
In contrast, Moderna’s mRNA vaccine uses genetic material to train the immune system to target four crucial viral antigens that enable the virus to attach to and infect cells. This innovative approach was previously demonstrated to be highly effective against COVID-19.
For the animal study, researchers vaccinated six macaques with Moderna’s mRNA vaccine and another six with the currently licensed live attenuated vaccine. A third group of six unvaccinated macaques served as controls.
Eight weeks post-vaccination, all animals were exposed to a lethal strain of mpox. Over the following four weeks, researchers monitored the animals’ health, assessing immune responses through blood samples.
The results were striking. All vaccinated macaques survived the exposure to mpox, whereas five of the six unvaccinated macaques succumbed to the virus. Notably, macaques that received the mRNA vaccine showed markedly better outcomes compared to those given the live attenuated vaccine.
They experienced significantly less weight loss and fewer lesions. The mRNA-vaccinated group developed up to 54 lesions, while those given the live attenuated vaccine had up to 607 lesions, and the control group had a maximum of 1,448 lesions.
Additionally, the mRNA vaccine reduced the duration of lesion presentation by more than ten days compared to the live attenuated vaccine. It also resulted in lower viral loads in both blood and throat swabs.
The mRNA vaccine, designated mRNA-1769, also demonstrated effectiveness in neutralizing other viruses within the Orthopox family, including vaccinia, cowpox, rabbitpox, camelpox, and ectromelia virus.
The vaccine candidate is currently undergoing an early-stage human clinical trial in the UK to further evaluate its safety and immune response.
