Officials say the virus is highly infectious in households with close contact, so the illnesses aren't unexpected.
The trial will be conducted in the Democratic Republic of the Congo in partnership with Emergent BioSolutions.
No one who was vaccinated was hospitalized with the viral disease.
The pledge came with at least $500 million in outbreak support, along with a plan to help bolster the domestic mpox vaccine supply.
The CDC reports just 2 new measles cases, raising the national total this year to 264.
The patient is a 66-year-old European man who had arrived in Thailand last week from an unspecified African country.
The agreement, using a new emergency funding mechanism, would secure 500,000 doses for delivery in 2024.
The Global Antibiotic Research and Development Partnership (GARDP) this week announced a partnership with Venatorx Pharmaceuticals to accelerate development of an investigational beta-lactam/beta-lactamase inhibitor combination for treating multidrug-resistant hospital infections.
In the region's other developments, Sierra Leone reported more cases, with the first two linked to the clade 2 global strain.
In other developments, the WHO says violence in the eastern DR Congo complicates the country's mpox response and that Azerbaijan has reported its first case.
Like other recent cases, the patient had traveled to Uganda, one of Africa's clade 1b mpox hot spots.
Close adherence to glove-wearing and other standard precautions likely protected residents, the authors say.
The pooled prevalence of conjunctivitis in mpox was 9%, followed by impaired vision (4%), keratitis (3%), and eye lesions (3%).
Contacts of the patient are being closely monitored and offered preventive vaccination.
In other developments, the recently identified clade 1a virus that has the APOBEC3 mutation, linked to more transmissibility, has been reported from Kinshasa.
So far this year Brazil has reported 52 cases of mpox, but all were clade 2.
In its monthly mpox update, the WHO said it is tracking several genetic developments, including rising cases of the rare 2b clade.
The freeze-dried Jynneos formulation will be easier to store and transport and will have a longer shelf life.
In Uganda, the virus is spreading in urban areas and among sexual networks, posing contact-tracing challenges.
Earlier patients had traveled to outbreak countries or were contacts of earlier cases.
Clade 1b is fueling a central Africa mpox outbreak, with the Democratic Republic of the Congo seeing the most cases.
The cases in Malawi bring the number of African countries affected by mpox to 23.
Healthcare workers remain the most trusted sources of information (73%), while trust in the federal government to provide factual information rose to 58%.
