Mpox Clade Ib Stirs Concern Across Europe
Health authorities are sounding the alarm as clues emerge that mpox, specifically the clade Ib strain, is circulating locally in several European nations. The UK Health Security Agency (UKHSA) has confirmed small numbers of clade Ib cases in Portugal, Spain, Italy, and the Netherlands, with additional cases reported in the United States. While mpox is usually mild, officials warn that the dynamics of this strain require heightened vigilance and vaccination adherence among eligible populations.
Who is Being Affected?
Official statements indicate that most of the newly identified clade Ib mpox cases have occurred among gay, bisexual, and other men who have sex with men (GBMSM). This population has not previously seen clade Ib transmission in the same way as other strains. In the United Kingdom, there are 16 confirmed clade Ib cases to date, all in England and described as unrelated to transmission within the GBMSM community. The discrepancy between geographic spread and transmission patterns highlights the complexity of mpox dynamics and the importance of vaccination for those who may be at higher risk due to behavior, travel, or exposure risk.
Vaccination: A Key Tool
Dr Katy Sinka, head of sexually transmitted infections at UKHSA, emphasized that the ongoing global spread of mpox underscores the value of vaccination for those who are eligible. “The ways in which we are seeing mpox continue to spread globally is a reminder to come forward for the vaccine, if you are eligible,” she said. The UK maintains a routine mpox vaccination programme targeting groups more likely to be exposed, including individuals with multiple sexual partners, those who participate in group sex, and people who visit sex-on-premises venues.
Effectiveness and Current Guidance
While there are no specific studies on vaccine effectiveness against clade Ib mpox, existing research indicates that the mpox vaccine offers about 75 to 80% protection against clade II mpox. Health officials caution that the effectiveness against clade Ib remains to be fully established, but vaccination remains a critical preventive measure. The UKHSA noted that, since the last technical assessment on 19 December of the previous year, the probability of importation of mpox into the UK has risen from medium to high. Nevertheless, the agency stated that the risk of onward transmission in the UK is still likely to be controlled to some degree by the GBMSM vaccination programme, and remains low to medium at present.
What This Means for Travelers and At-Risk Populations
Mpox tends to be a mild infection for many, but experiences can vary. The UKHSA stresses that clade Ib and clade Ia mpox are no longer classified as high-consequence infectious diseases, though severe cases can occur. This reality reinforces the importance of preventive measures, particularly for people who are more likely to be exposed through sexual networks or international travel. The agency also points to the value of staying up to date with vaccination before attending large Pride events or international gatherings, where the risk of exposure may be higher.
Public Health Messaging and Community Action
Public health groups are calling for proactive vaccination as part of broader efforts to curb mpox transmission. In Europe and beyond, charities and health organizations advocate for timely vaccination, routine testing where appropriate, and clear guidance for those planning travel to autumn and winter Pride events. As mpox continues to appear in new locations, individuals who are eligible should assess their risk and seek vaccination through approved clinics and health services.
Bottom Line
The emergence of mpox clade Ib in Europe highlights the evolving landscape of mpox transmission. While the overall risk to the general population remains relatively low, targeted vaccination remains a well-supported strategy to reduce transmission and protect those at higher risk. Health authorities urge eligible individuals to get vaccinated, remain informed about local guidance, and consider vaccination ahead of major events where exposure may increase.
