French health authorities on Friday urged preemptive vaccination against monkeypox for certain segments of the population, especially those with multiple sexual partners.
"Men who sleep with men and transgender people with multiple sexual partners, sex workers and people working in places where people go to find sex" were among "the groups most exposed to the virus," the HAS body said in a statement.
On top of existing advice to offer the vaccine following a confirmed monkeypox infection or at-risk contact, the top advisory body now "recommends offering pre-exposure vaccination" to all three groups.
With 577 cases of monkeypox found in France -- 387 in the Ile-de-France region which includes capital Paris -- and under pressure from LGBTQ and health groups, the health ministry had last week asked the HAS to review the vaccination guidelines.
Monkeypox causes fever, headaches, muscle and back pain for days before rashes, lesions, spots and finally scabs appear on the skin.
There has been a surge in infections since early May outside the West and Central African countries where the disease has long been endemic.
The World Health Organization said on Thursday men who sleep with men accounted for three in five of the more than 6,000 confirmed monkeypox infections it had collated from 59 countries.
Genome testing indicates the current outbreak is of a West African form of monkeypox, milder than the Congo Basin group.
French data showed by early July, men engaging in homosexual sex accounted for 97 per cent of the cases where data on the patients' sex lives was available.
And 75 per cent were among people who had had multiple partners in the weeks before the infection was detected.
The HAS recalled that monkeypox can be transmitted by skin-to-skin contact by people already exhibiting rash or scabs, as well as via saliva and respiratory droplets.
People can be at risk from touching the damaged skin of an infected person or from spending more than three hours within two metres of them, it said.
The ease of transmission makes contact tracing chains of infection difficult, especially in cases where people have had anonymous sex.
"Faced with the spread of the virus, the kinetics of the epidemic and the difficulty tracing contacts," targeted preemptive vaccination was the best option, the HAS concluded.
But it added that for health workers caring for those with monkeypox "routine hygiene measures and wearing personal protective equipment makes the risk of infection very low", advising vaccines only "on a case-by-case basis".