Supplies of a vaccine that protects against monkeypox are to be stretched by giving people smaller doses, UK public health officials have announced.
As the monkeypox outbreak continues around the world, efforts are being made to vaccinate those most at risk. However, supplies of the jab, initially developed to tackle the more serious but eradicated disease smallpox, are limited.
In July the UK ordered an additional 100,000 doses of the Imvanex smallpox vaccine, also known as Jynneos, which is manufactured by Bavarian Nordic. These are expected to arrive next month. In the meantime, concerns have been raised that the UK is close to exhausting its current supplies.
Now the UK Health Security Agency (UKHSA) has announced that it will trial offering eligible patients smaller doses of the vaccine, a move it says could allow five times as many people to be protected.
The agency noted that studies suggest smaller doses generate “a near-identical” immune response compared with full doses, and the approach has been used in other viral outbreaks around the world when vaccine supplies are tight.
“Global supplies of the smallpox vaccine used to combat monkeypox are limited but we acted early to ensure the UK obtained the maximum number of doses available,” said Dr Mary Ramsay, the head of immunisation at the UKHSA.
“Adopting this tried and tested technique will help to maximise the reach of our remaining stock, including the 100,000 doses due to arrive in the country next month, potentially enabling us to offer protection for many more thousands of people. We will continue to remain agile in our response to the monkeypox outbreak and will adapt our approach as new science and advice becomes available.”
The approach, in which recipients aged 18 and over are given 0.1ml of the vaccine rather than the full 0.5ml dose, is being trialled in a sexual health clinic in Manchester from Monday, with two clinics in London set to follow suit.
UKHSA said eligibility for vaccination before exposure remained unchanged – encompassing gay, bisexual and other men who have sex with men who meet criteria such as having a recent history of multiple partners or participating in group sex.
However, it was limiting the offer of vaccination after exposure to monkeypox to those most at risk of severe illness, such as people with immunosuppression, children under the age of five and pregnant women. These groups will, at present, continue to receive the full dose of the vaccine.
Dr Will Nutland, an honorary assistant professor at the London School of Hygiene & Tropical Medicine and a co-founder of PrEPster, said the use of smaller doses was pragmatic and welcome.
“Communities we are engaging with are keen to receive vaccination as soon as possible, and the pilots provide the opportunity to understand the acceptability and feasibility of providing vaccination this way,” he said.
“Evidence shows that fractional dosing, when correctly administered, is as effective as the vaccination method currently in use. We must now collectively move to ensure that those who are given the opportunity to receive vaccination are fully informed and are confident to come forward when invited.”
