WHO adds first mpox vaccine to prequalification list

The decision is expected to facilitate timely access to Bavarian Nordic’s Imvanex

The World Health Organization (WHO) has announced that it has added Bavarian Nordic’s mpox vaccine to its list of prequalified vaccines.

The decision is expected to facilitate timely and increased access to Imvanex (MVA-BN), which is now the first mpox vaccine to be prequalified by the organisation.

More than 120 countries have confirmed over 103,000 cases of mpox, a disease with symptoms similar to smallpox, since the onset of the global outbreak in 2022.

Originally developed as a smallpox vaccine in collaboration with the US government, Imvanex can be administered in individuals aged 18 years and over as a two-dose injection given four weeks apart, WHO said.

The organisation has also recommended single-dose use in supply-constrained outbreak situations, but has emphasised the need to collect further data on vaccine safety and effectiveness in these circumstances.

While the vaccine is not currently licensed for those aged under 18 years, it may be used “off-label” in infants, children and adolescents, as well as in pregnant and immunocompromised people in outbreak settings where the benefits of vaccination outweigh the potential risks.

The new prequalification status means governments and international agencies such as Gavi and Unicef can procure the vaccine for eligible countries.

WHO’s assessment was supported by available data showing that a single dose of Imvanex given before exposure has an estimated 76% effectiveness in protecting people against mpox, while the two-dose schedule achieved an estimated 82% effectiveness.

WHO director-general, Dr Tedros Adhanom Ghebreyesus, said: “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.

“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.”