An investigation has been launched in France after 59 per cent of people in a new monkeypox cluster claimed to be fully vaccinated.
While the jab does not offer complete protection against the disease, usually only 25 per cent of French cases are in vaccinated individuals.
The high vaccine rate in the Centre-Val de Loire cluster – 10 of 17 – has sparked fears of a mutation.
Monkeypox – now officially named mpox – causes a blistering rash, fever, chills, exhaustion, and muscle aches. It is passed from person to person through close physical contact, and touching infected clothing, bedding or towels.
While most commonly found in west and central Africa, the disease made headlines in 2022 when an outbreak was declared across Europe and the US.
Since spring 2022, a total of 25,843 cases have been identified across the European region, mostly among men who have sex with men. Globally, more than 85,000 cases have been reported in locations that have not historically recorded the disease.
Those affected in the current French cluster are all men aged between 24 and 56.
“No parties or events common to the cases have been identified,” the French health authority said. “No person has required hospitalisation.”
The investigation could throw up several possible explanations, according to Dr Michael Marks, Associate Professor at the London School of Hygiene and Tropical Medicine.
“First we need to understand when these individuals were vaccinated and with what dose,” Dr Marks said. “We know it takes a number of weeks for the body to mount a response and that translates to protection. When did they have the vaccine?”