Mpox warning: Vaccines might not protect against deadly new viral strain spreading rapidly, say experts

Vaccines hailed as primary hope of stopping a now global mpox outbreak of a new deadlier strain may not even work, scientists have warned.    

Professor Marion Koopmans, director of the pandemic and disaster Centre at the Erasmus Medical Centre in The Netherlands said experts just don’t know how the new clade 1b mpox virus would react to current jabs. 

‘The honest answer is we do not know yet,’ she said. 

Current mpox vaccines were used during the 2022 global outbreak against the milder strain of the virus, known as clade 2.

But they have yet to be tested against the more potent version that’s swept across Africa and has now been spotted in Europe and Asia.

And experts are not even sure exactly how much protection they provided against the 2022 outbreak.  

The jab is, in fact, the vaccine given to prevent smallpox, a close relative of mpox.  

Due to the similarity between the two viruses, experts believed it would be effective — which is known as cross-protection. 

However, as it was deployed during a live outbreak, it was hard to unpick exactly what benefit it provided, says Prof Koopermans. 

During the 2022 outbreak, gay and bisexual men — the group mpox primarily hit — is believed to have taken other measures to reduce their risk, such as limiting the number of new sexual partners. 

‘There is some evidence for clinical efficacy during the vaccinations were given during an evolving outbreak when there are also other things that people do that reduce transmission,’ Professor Koopmans told journalists. 

‘It’s not so easy to say is this full-vaccine protection.

‘The hope is that for clade 1b there would also be sufficient cross-protection, but that’s an area with an urgent study need.’

Professor Dimie Ogoina, an expert in infectious diseases at Niger Delta University who also spoke at the event, added another factor that would be challenge a potential mpox vaccine rollout in Africa is who gets it first. 

‘Any vaccine strategy should be informed by your understanding of the epidemiology of the disease in your region,’ he said,. 

‘I’m not sure we fully understand the transmission dynamics and risk factors for mpox in many parts of Africa.’

Like Professor Koopmans he also highlighted the uncertainties regarding the effectiveness of the current mpox vaccines. 

‘The vaccine effectiveness studies that have been done were done in the global North for clade 2b and amongst gay and bisexual men,’ he said. 

‘One cannot (guarantee) to say the effectiveness was based fully on the vaccine alone.

‘Some studies have shown behavioural change was responsible for the decline in mpox cases in parts of Europe and America, while vaccines also helped.’

Professor Ogoina added there were also uncertainties such as how long the vaccines offered protection and how effective they were in children who seem particularly at risk in the new outbreak 

‘We have not replicated these studies in children and that is a great challenge especially in the DRC (Democratic Republic of the Congo) where the majority of people impacted significantly are children,’ he said. 

‘We should use a risk/benefit approach, especially in an outbreak setting, in whether children should be vaccinated.’

But Professor Placide Mbala Kingebeni, an expert in epidemiology at the Clinical Research Center at the National Institute of Biomedical Research in the DRC, the nation hit hardest be the ongoing outbreak, said jabs remained ‘the best tool we have’. 

‘Even if we don’t have all the data regarding the efficacy, this is something we should do,’ he said. 

The new strain of mpox, formerly called monkeypox, is far deadlier than the mild strain which spread to over a dozen countries, including the UK in 2022.

Designed clade 1b mpox, it kills about one in 20 adults it infects but the mortality rate rises to one in 10 in children. 

The virus spreads primarily through skin-to-skin contact which can include sex or through direct care, for example mother to child. 

Clade 1b has swept through central Africa killing hundreds since the outbreak began. 

In just the past few weeks cases of the new strain have been detected in Sweden and Thailand meaning it has now reached both Europe and Asia. 

While no cases have yet been confirmed in the UK experts suspect the new variant is already in Britain as it can take over two weeks for symptoms like the classic skin lesions to develop.  

But experts have said fatality rates for clade 1b from central Africa are unlikely to be replicated in developed nations due to better access to higher quality healthcare. 

The UK Health Security Agency (UKHSA) has already cautioned it is ‘already planning’ for UK cases of the new strain.

It comes as the World Health Organization said it needs over £66million ($87million) over six months to stop the current mpox outbreak. 

Mpox typically causes characteristic lumpy lesions, as well as a fever, aches and pains and fatigue.

In a small number of cases, it can enter the blood and lungs, as well as other parts of the body like the brain which causes it to become life-threatening.