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Madagascar forced to divide and share mpox vaccine as epidemic takes off
The African island is currently battling its largest-ever outbreak of the virus formerly known as monkeypox
Maeve Cullinan Global Health Security Reporter Show biography
Published 11 August 2026 1:29pm BST
Authorities in Madagascar are being forced to split single vaccines into fifths to try to protect as many people as possible during an ongoing mpox outbreak.
The method, known as “fractional dosing”, is authorised by the World Health Organization (WHO) in emergencies when there are critical vaccine shortages, but is not routinely recommended and carries a level of risk.
Madagascar, the African island with a population of roughly 33 million people, is currently battling
its largest-ever outbreak of the virus formerly known as monkeypox, with at least 4,000 cases recorded so far.
Another one million people are thought to be at risk of contracting clade 1b mpox, a fast-spreading strain of the virus
that emerged from the Democratic Republic of the Congo in late 2023.
High risk groups include sex workers, young children, and people living with HIV/Aids. Medical workers are also at risk.
“Public health authorities in Madagascar have been given too few doses to protect the at-risk population; they were initially given 30,000 doses in May, and a subsequent 30,000 have just arrived at the end of July,” said Akhil Bansal, a doctor of internal medicine working on the mpox response in Madagascar and a policy fellow at the Centre for Global Development
.
“However, we need to vaccinate more than one million people, so we have been “fractionally dosing”, or splitting vaccines, into fifths, to stretch the supply as far as we can.
“This is a somewhat established approach for vaccines, but even then, the number of doses we have is insufficient,” said Dr Bansal.
The WHO has previously endorsed fractional dosing, where vials of vaccine are divided into smaller parts, during health emergencies.
The approach – which was used in the UK during Covid – is generally considered a safe and effective way of protecting populations when vaccine supplies are limited.
The method was authorised during yellow fever outbreaks in Angola and the Democratic Republic of the Congo, and was also used for mpox vaccines in the US and UK in the summer of 2022, during an outbreak involving a different strain of the virus that primarily affected gay and bisexual men.
Several clinical trials have found that, when administered correctly, fractional doses of mpox vaccine can provide protection comparable to full doses. But the approach also carries associated risks.
One concern is the need for thousands of extra needles and syringes, increasing the risk of accidental needle re-use and the transmission of blood-borne infections such as HIV.
“Madagascar has had to acquire many more needles and syringes because normally one dose is attached to one vaccine,” said Dr Bansal.
Fractional doses of a standard vaccine must be administered intradermally – into the top layer of the skin – rather than into the muscle. The skin contains specialised immune cells that can trigger a strong immune response, allowing smaller quantities of vaccine to be used.
But intradermal injections are considerably more difficult to administer than injections into the muscle. They require skilled vaccinators to ensure the vaccine is delivered at the correct depth.
They are also more likely to cause local reactions, including swelling and itching, and can sometimes leave a distinctive raised “wheel” on the skin – similar to the scars left by the BCG vaccine for tuberculosis which many people received as children before the disease was eradicated in the UK in 1980.
Public health officials within Madagascar remain hopeful that they will receive additional vaccine supplies in the coming months, helping to curb an epidemic that has overwhelmed local hospitals and clinics over the past four months.
But mpox vaccines are expensive, costing between $50 and $140 per dose, and can be difficult to procure in low-income countries such as Madagascar, which is the world’s fifth-poorest country.
The 60,000 doses delivered to the island so far have been funded largely by Gavi, the Vaccine Alliance, and the WHO.
Both organisations have faced significant funding shortfalls over the past year as governments, including those of the UK and US, have reduced their spending on global health.
Mpox typically causes flu-like symptoms and a painful rash of swollen lesions that can spread across the entire body.
For people living with HIV, the virus is particularly dangerous and can lead to severe complications, including brain inflammation, severe bacterial infections of lesions and, in rare cases, can result in death.
It spreads mostly through very close physical contact, including sexual contact and through sharing towels and bed sheets.
In poor countries, where people often live in closer quarters and have less access to simple infection control measures like soap and clean water, outbreaks can be particularly difficult to control.
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