Mpox Reinfections Occur Regardless of Vaccination

Since May 2022, a global outbreak of human mpox has proven to differ from the 2017–18 outbreak in Nigeria. The mpox strain responsible, Clade IIb, has mutated substantially, according to a study published in the peer-reviewed journal The Lancet Infectious Disease.

On September 4, 2023, this research study confirmed recent mpox cluster cases were described in individuals with presumed immunity through recent infection or vaccination. 

These researchers found that of 37 men who have sex with men, seven individuals had mpox reinfections, and 29 individuals had mpox infections that occurred after two appropriately spaced JYNNEOS-Bavarian Nordic vaccine courses.

And one individual had an infection that met the criteria for both reinfection and infection after vaccination.

Those men, with an average of 36, with natural immunity after initial infection had a shorter disease course with less mucosal disease upon reinfection than with their initial infection.

Few lesions, minor mucosal disease, and minimal analgesia requirements characterized Mpox infections post-vaccination.

Overall, there were no deaths or bacterial superinfections, and all individuals were managed in the ambulatory clinic, with one hospital admission for a necrotizing neck lesion reported in the study.

As of May 2023, about 87,500 mpox cases and 141 related deaths were reported from 111 World Health Organization member countries.

Previous studies from the Netherlands, Spain, England, and the United States have described infections among children and adolescents during the recent mpox outbreak. 

Globally, 1.3% of reported cases have been in children and adolescents.

This finding differed from 1970–2021 when mpox cases in Central Africa were predominately (54%–90%) reported in young children (ages 4–6).

For patients without known exposure to a person with mpox, various activities and interactions with others were reported in a separate study.

However, it was impossible to determine the likely source of infection for most of them, wrote these researchers. These highlight concerns about a potential mpox resurgence and have underscored the need to address critical knowledge gaps concerning immunity.

Previous mpox studies have been posted since 2022.