In July 2022, the World Health Organization (WHO) declared a Public Health Emergency of International Concern (PHEIC) due to a rapid multi-country outbreak of mpox, primarily spreading through sexual contact in regions previously unaffected. This emergency status was lifted in May 2023 after a global decline in cases. However, the emergence of a new Clade Ib and a resurgence of mpox cases in Africa led the WHO to declare another PHEIC on August 14, 2024. The current outbreak poses risks to high-risk groups, including pregnant women and children under 18, including infants.
The WHO’s Global Advisory Committee on Vaccine Safety (GACVS) previously reviewed the safety of three mpox vaccines—MVA-BN, LC16m8, and ACAM2000—during a joint meeting in December 2022. Recent updates on safety data for the modified vaccinia virus (MVA)-BN and minimally replicating LC16m8 vaccines were shared on September 20, 2024.
Given that MVA-BN is non-replicating and can be administered to pregnant women, Bavarian Nordic has developed a risk management plan for its use in African nations. The GACVS supports further clinical studies addressing vaccine safety in infants, children aged 2 to 12, and pregnant women.
Current post-approval data indicate that the vaccines have favorable safety profiles, but close monitoring is essential for detecting any safety signals. The administration methods for mpox vaccines vary, necessitating special training for healthcare workers, especially for the LC16m8 vaccine, which requires intradermal injection techniques.
The GACVS also discussed preparations for safety monitoring post-vaccine introduction, emphasizing the need for a standardized protocol for early safety signal detection. Safety monitoring is crucial for both MVA-BN and LC16m8, particularly for high-risk groups, including infants, immunocompromised individuals, and pregnant women.
The committee encourages the use of reporting tools like Vigiflow, VigiMobile, and the Med Safety App to facilitate spontaneous reporting of adverse events. Comprehensive surveillance and studies are recommended to identify rare adverse events that clinical trials may not have detected.
Lastly, the committee highlighted challenges in applying restrictions on vaccine use for people living with HIV, particularly those with low CD4 cell counts. It stressed the importance of effective communication regarding the risks and benefits of vaccination while ensuring thorough safety monitoring in high-prevalence HIV populations.
