The infected person exposed 17 people at 2 group homes to the disease.
The test the US Centers for Disease Control and Prevention uses to identify clade I mpox cases is 'most likely not reliable' for detection of the substrain identified in the study, the authors say.
Another mpox study today showed that dose-sparing vaccine administration of the Jynneos vaccine appeared to have worked.
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The study's safety board recommended halting enrollment after an assessment showed the chance was less than 1% that the study would demonstrate efficacy if completed.
Recent detections in Zimbabwe and Zambia were confirmed as the novel 1b clade.
UK health officials said the overall threat to the UK population remains low.
Seven countries outside of Africa have now reported imported clade 1b cases.
Some of the group's concerns include rising case numbers, expanding spread, and response challenges.
The vaccine will allow younger children, vulnerable to infections from household contact, to be immunized.
The California case makes the United States the sixth country outside of Africa to report an imported clade 1 case.
Meanwhile, amid a steep rise in Uganda, health officials have identified new mpox clusters in sex workers.
Meanwhile, Uganda’s outbreak is rapidly expanding, mostly involving intimate close-contact spread and among sexual networks.
The trial will be conducted in the Democratic Republic of the Congo in partnership with Emergent BioSolutions.
