Mpox: WHO prequalifies first vaccine

The prequalification approval is expected to facilitate timely and increased access to this vital product in communities with urgent need, to reduce transmission and help contain the outbreak. WHO’s assessment for prequalification is based on information submitted by the manufacturer, Bavarian Nordic A/S, and review by the European Medicines Agency, the regulatory agency of record for this vaccine.

“This first prequalification of a vaccine against mpox is an important step in our fight against the disease, both in the context of the current outbreaks in Africa, and in future,” said WHO Director-General Dr Tedros Adhanom Ghebreyesus. “We now need urgent scale up in procurement, donations and rollout to ensure equitable access to vaccines where they are needed most, alongside other public health tools, to prevent infections, stop transmission and save lives.”

The MVA-BN vaccine can be administered in people over 18-years of age as a 2-dose injection given 4 weeks apart. After prior cold storage, the vaccine can be kept at 2–8°C for up to 8 weeks.

“The WHO prequalification of the MVA-BN vaccine will help accelerate ongoing procurement of the mpox vaccines by governments and international agencies such as Gavi and Unicef to help communities on the frontlines of the ongoing emergency in Africa and beyond,” said Dr Yukiko Nakatani, WHO Assistant Director-General for Access to Medicines and Health Products. “The decision can also help national regulatory authorities to fast-track approvals, ultimately increasing access to quality-assured mpox vaccine products.”

The WHO Strategic Advisory Group of Experts (SAGE) on Immunization reviewed all available evidence and recommended the use of MVA-BN vaccine in the context of an mpox outbreak for persons at high risk of exposure. While MVA-BN is currently not licensed for persons under 18 years of age, this vaccine may be used “off-label” in infants, children and adolescents, and in pregnant and immunocompromised people. This means vaccine use is recommended in outbreak settings where the benefits of vaccination outweigh the potential risks.

WHO also recommends single-dose use in supply-constrained outbreak situations. WHO emphasizes the need to collect further data on vaccine safety and effectiveness in these circumstances.

Available data shows that a single-dose MVA-BN vaccine given before exposure has an estimated 76% effectiveness in protecting people against mpox, with the 2-dose schedule achieving an estimated 82% effectiveness. Vaccination after exposure is less effective than pre-exposure vaccination.

Good safety profile and vaccine performance has been consistently demonstrated in clinical studies, as well as in real-world use during the ongoing global outbreak since 2022. In light of the changing epidemiology and emergence of new virus strains, it remains important to collect as much data as possible on vaccine safety and effectiveness in different contexts.

Since the triggering of the emergency use listing for mpox vaccines by WHO Director-General on 7 August 2024, WHO has conducted product and programmatic suitability assessments of MVA-BN vaccine.

“The findings of the assessments are particularly relevant in the context of the declaration of a public health emergency of international concern (PHEIC) related to the upsurge of mpox in Africa,” said Dr Rogerio Gaspar, WHO Director for Regulation and Prequalification. “We are progressing with prequalification and emergency use listing procedures with manufacturers of two other mpox vaccines: LC-16 and ACAM2000. We have also received 6 expressions of interest for mpox diagnostic products for emergency use listing so far.”

The escalating mpox outbreak in the Democratic Republic of the Congo and other countries was declared a PHEIC by the WHO Director-General on 14 August 2024.

Over 120 countries have confirmed more than 103 000 cases of mpox since the onset of the global outbreak in 2022. In 2024 alone, there were 25 237 suspected and confirmed cases and 723 deaths from different outbreaks in 14 countries of the African Region (based on data from 8 September 2024).