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Mpox is less severe if people have been vaccinated

Hester Phillips

17 October 2023

Data from nine countries suggests people who are vaccinated against mpox can still get it – but their symptoms will be much milder

Doctor's hand in a medical glove holds a bottle with Vaccine Monkeypox and Smallpox
Photos are used for illustrative purposes. They do not imply health status or behaviour. Credit: iStock/Chalffy

The importance of enabling gay men and other men who have sex with men to get vaccinated against mpox has been highlighted by a new, multi-country study. 

What is the research about? 

The research looked at the effect of mpox vaccinations and previous infections on the severity of symptoms.  

Since May 2022, there has been a global outbreak of mpox. Around 87,000 cases have been reported in 111 countries, mainly in Europe, the UK, North America and Latin America. Gay men and other men who have sex with men are most affected.  

Why is this research important? 

If people have been vaccinated against mpox, or have had mpox before, they will have some immunity. What this immunity means in relation to the mpox strain that caused the 2022 outbreak is being studied. This research adds to the evidence. Hospitals involved in the SHARE-net initiative provided data on people who got mpox between May 2022 and June 2023 after previously being infected in 2022 or vaccinated. 

What did they find out?  

The study identified 37 people who got mpox after being vaccinated or previously infected. All were cisgender gay or bisexual men. The reported cases were in Argentina, Canada, France, Italy, Israel, Mexico, Spain, the USA and the UK. Eight of the infections were reinfections, the remaining were infections after vaccination. 

Symptoms were milder among people who had been vaccinated than those who were reinfected, but both were less severe than getting mpox without any immunity. People had fewer skin lesions, fewer areas of the body affected, less severe mouth and genital infections and fewer secondary infections. They were also far less likely to need pain relief or hospitalisation, and no deaths occurred. 

People who had previously had mpox recovered around a week faster the second time around.  

Most of the men in the study (86%) had multiple male partners, and 95% either did not use condoms or did not use them consistently. Around one-third (32%) had a sexually transmitted infection. Eight people had HIV, all of whom were virally suppressed.  

What does this mean for HIV services? 

Gay men and other men who have sex with men who are at heightened risk of mpox need to get vaccinated. This includes gay men and other men who have sex with men in countries that were already affected by mpox before the 2022 outbreak, and newly affected countries that still have no access to vaccines.  

There is a need to advocate to policy-makers to ensure people who most need the mpox vaccine can get it. As people with advanced HIV are at risk of particularly serious symptoms from mpox, gay men with HIV should be among the first people prioritised.  

It is also important to raise awareness with healthcare professionals so they know that previous mpox infection and/or vaccination will not stop someone from getting mpox. This might help people with mpox get diagnosed and treated faster, rather than their symptoms being mistaken for something else. 

If mpox vaccines are available, it will be important to run clear, fact-based communication campaigns, to ensure the right people come forward. These should be developed with and for the groups most at risk of mpox in your area. 

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