Groundbreaking Study Reveals Vaccine Discrepancies

A groundbreaking study published in The Lancet Infectious Diseases has unveiled alarming discrepancies in the effectiveness of Bavarian Nordic’s Jynneos vaccine for mpox, particularly among HIV-positive individuals. Conducted at Charité Universitätsmedizin Berlin, the study included over 6,000 participants—specifically men who have sex with men and transgender individuals aged 18 and older. The results show that while the vaccine is 84% effective in those without HIV, its effectiveness plummets to just 35% in those living with the virus. This stark contrast underscores the pressing need for targeted prevention strategies for the most vulnerable populations.

Understanding Mpox and Its Impact

Mpox, a viral illness characterized by symptoms including fever, muscle aches, a blistering rash, and swollen lymph nodes, is transmitted via close contact with infected individuals, animals, or contaminated objects. Although healthy individuals often experience mild symptoms, those with compromised immune systems, such as individuals with uncontrolled HIV, face a heightened risk of severe complications, hospitalization, and even death.

Current Status of Mpox Outbreaks

As reported by the US Centers for Disease Control and Prevention (CDC), the ongoing Clade II 2022 mpox outbreak has registered more than 100,000 infections across 122 countries, affecting North America, South America, Europe, Asia, Africa, and Australia. Fortunately, Clade II has demonstrated an impressive survival rate exceeding 99%. However, Clade I, which has been causing outbreaks in Central and Eastern Africa since 2024, is notorious for its association with severe illness and has already accounted for over 21,000 infections.

Jynneos Vaccine Efficacy and Recommendations

Jynneos, also known as Imvanex, is approved as a two-dose vaccine in the US and Canada for high-risk individuals aged 18 and older. In contrast, it is authorized for individuals as young as 12 in Europe. The reduced efficacy observed in HIV-positive patients may be linked to diminished T-cell responses post-vaccination compared to their HIV-negative counterparts, emphasizing the critical need for these individuals to complete the full two-dose regimen.

Other Vaccine Options and Trials

In the realm of mpox prevention, Jynneos is not alone; GlobalData reports only two other vaccines approved for mpox: KM Biologics’ mpox LC16m8 and Emergent BioSolutions’ ACAM2000. Notably, the LC16m8 vaccine has been shown to be safe and effective in those with well-controlled HIV. Additionally, there are three other mpox vaccines currently undergoing clinical trials, including LC16m8—investigated by the National University of Colombia—BioNTech’s BNT-166a, and Moderna’s mRNA-1769.

Vaccine Safety and Reactogenicity

The study involving Jynneos evaluated vaccine safety and reported local reactions in 70% of participants after the first dose, dropping to 57% after the second. Systemic reactions were observed in 22% and 18%, respectively. Interestingly, individuals with HIV experienced fewer local reactions—62% after the first dose and 52% after the second—compared to 74% and 59% in those without HIV. These findings indicate that reactogenicity, or the occurrence of side effects, is indeed reduced among individuals with HIV, aligning with the vaccine's lower effectiveness in this group.

Need for Continued Research and Attention

As the mpox pandemic continues to pose significant public health challenges, these newly available data about the safety and effectiveness of Jynneos brings urgent attention to the critical need for further research on mpox prevention specifically targeting HIV patients. It is imperative for the global health community to focus attention on developing more effective vaccination strategies to protect these high-risk populations from future outbreaks. What could the consequences be if we fail to address these gaps? Only time will tell, but the stakes have never been higher.