McMaster drug trial receives more than $6m to test smallpox vaccine against mpox

Children accounted for the majority of mpox cases and deaths in the DRC since June 2023

Researchers from McMaster University have received $6.7m from the Coalition for Epidemic Preparedness Innovations (CEPI) and the Canadian Institutes of Health Research to assess the effectiveness of a smallpox vaccine in providing protection against mpox after post-exposure.

Beginning in August, the Smallpox Vaccine for Mpox Post-Exposure Prophylaxis: A Cluster Randomized Controlled Trial (SMART) will assess the effectiveness of the Bavarian Nordic smallpox vaccine, MVA-BN, in more than 1,500 participants in households with laboratory-confirmed mpox infection at sites in the Democratic Republic of Congo (DRC), Uganda and Nigeria.

Mpox is a disease caused by infection with a virus known as the monkeypox virus, which is part of the same family as the virus that causes smallpox. Symptoms include fever and headache, as well as painful lesions. In some cases, the disease can lead to bronchopneumonia, sepsis, encephalitis, loss of vision and even death.

In the DRC, between June 2023 and 2024, over 7,000 suspected and confirmed cases and more than 300 deaths have been reported, with children accounting for the majority.

The current outbreak mpox strain, known as Clade I, is estimated to be fatal in up to 12% of cases.

The MVA-BN vaccine is currently administered to individuals who are at high risk of exposure to mpox, such as healthcare workers, to provide protection. However, in resource-scarce areas, a post-exposure mpox vaccination could potentially defuse it and help people recover more quickly.

Selected participants will be given a post-exposure vaccination of the MVA-BN smallpox vaccine or control vaccine and, after four weeks, scientists will compare the number of participants who contract mpox in each group and will follow up on patients who become sick to measure the severity of their symptoms.

Researchers believe that the evidence generated from the trial could help shape mpox vaccination strategies to tackle mpox outbreaks in the DRC and neighbouring countries.

Richard Hatchett, chief executive officer, CEPI, commented: “While healthcare workers typically vaccinate somebody before they are at risk of an infection, post-exposure-vaccinations allow for a more targeted approach, minimising [the] use of vaccine supply.”