Mpox Clade Ib: A new reminder for vaccination
Health authorities in Europe are raising alarms as the mpox (monkeypox) landscape shifts with the emergence of clade Ib cases in several countries. While mpox has historically affected different populations, recent reporting shows small numbers of clade Ib infections in Portugal, Spain, Italy, the Netherlands, and the United States. The UK Health Security Agency (UKHSA) notes that the majority of newly identified infections have occurred among gay, bisexual and other men who have sex with men (GBMSM), a group where clade Ib transmission had not previously been observed.
What we know about clade Ib
Clade Ib is a lineage of mpox that, for now, appears to be circulating in small clusters. There are 16 confirmed clade Ib cases in the UK, all in England and not linked to transmission within the GBMSM community. The UKHSA emphasizes that the current pattern of spread across borders underlines the importance of vaccination for eligible individuals, regardless of appearance of local clusters. Dr Katy Sinka, head of sexually transmitted infections at UKHSA, said the ongoing global spread is a reminder to come forward for vaccination if you are eligible.
Vaccination: the best defense
The UK maintains a routine mpox vaccination program for those at higher risk, including people with multiple sexual partners, individuals who participate in group sex, and attendees of sex-on-premises venues. While there are no definitive studies on vaccine effectiveness against clade Ib specifically, existing data suggest mpox vaccines are about 75–80% effective against clade II mpox. Public health experts stress that vaccination is a practical tool to reduce transmission, protect at-risk groups, and mitigate potential outbreaks as the virus moves between regions.
How officials assess risk and respond
According to UKHSA, the probability of importation of mpox into the UK has increased from medium to high since the last technical assessment. Still, they assess the risk of onward transmission within the UK as low to medium, largely due to the protection afforded by the GBMSM vaccination program and existing surveillance systems. Mpox generally causes a mild illness, and clade Ib and la strains are no longer classified as high-consequence infectious diseases; however, severe outcomes can occur in some individuals. Health authorities stress that vigilance, testing, and vaccination are essential components of containment—and that travel or attendance at large events, especially during Pride season in autumn and winter, may heighten exposure risk.
Public guidance and next steps
Charities and health groups have urged people planning autumn Pride travels to consider vaccination ahead of travel and crowded events. Eligible individuals should check their local health authority guidelines to determine if they qualify for mpox vaccination and how to access shots. Health officials also encourage people to monitor symptoms—such as fever, rash, or swollen lymph nodes—and seek testing promptly if mpox is suspected. A proactive vaccination strategy, combined with continued surveillance, remains the strongest defense against the spread of clade Ib mpox as Europe navigates evolving patterns of transmission.
Bottom line
As mpox evolves across borders, vaccination offers a practical protective measure for those most at risk. The best course is to stay informed through official health channels, verify eligibility, and get vaccinated if advised. The concerted effort from public health agencies, clinics, and community organizations aims to curb transmission and protect vulnerable populations across Europe.
