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 strain would react to current jabs.
‘The honest answer is we do not know yet,’ she said.
Current mpox vaccines, which were used during the 2022 global outbreak of milder strain of the virus have been shown to work but have yet to be tested against the more potent version sweeping Africa.
Professor Koopmans as the vaccines, which are based on a close relative of mpox to provide protection, had been deployed during a live outbreak it was hard to unpick exactly how effective the vaccine was.
This was because people at risk of virus in the 2022 outbreak, which primarily hit gay and bisexual men, may have proactively taken 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.
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.