Monkeypox: Smaller vaccine doses to be trialled in UK to make supplies go further

A medical professional prepares a dose of the monkeypox vaccine on July 23, 2022 in London, England.

The UK will begin stretching out monkeypox vaccines by delivering “smaller but equally effective doses”, the UK Health Security Agency (UKHSA) has announced.

A pilot programme will begin on Monday (22 August) at a Manchester sexual health clinic and will be extended to two clinics in London shortly afterwards.

The approach, designed to stretch supplies to protect more people, is known as “fractional dosing”, and has been “commonly used in other worldwide outbreaks when vaccine supplies are constrained”, the UKHSA said.

In clinics trialling the new approach, those eligible for vaccination will be offered a 0.1ml dose of the smallpox vaccine Jynneos, instead of the typical 0.5ml, which should produce a “near-identical immune response in patients”.

Fractional dosing, which has already been approved by the US Federal Drug Administration and the European Medicines Agency Emergency Task Force in their monkeypox vaccine roll-out, could mean that vaccines reach five times as many people.

In the UK, nearly 3,200 cases of the virus have been confirmed.

Those eligible for pre-exposure vaccination include men who have sex with men, especially those who have multiple partners and participate in group sex, as well as workers in healthcare and ‘sex on premises’ settings that may be exposed to the virus.

As well as using fractional dosing, the UKHSA said that it has updated post-exposure vaccine eligibility to make sure doses are “reserved for those close contacts who are at highest risk of severe illness” because of limited vaccine supply.

Dr Mary Ramsay, head of immunisation at UKHSA, said: “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.

“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.”

Deborah Gold, chief executive of National AIDS Trust, added in a statement: “We welcome UKHSA’s exploration of fractional dosing for monkeypox.

“If rolled-out, this will increase the number of at-risk people getting a monkeypox vaccine, and should mean the supplies the UK has will meet immediate need, helping to address global vaccine supply issues.

“Progress on vaccine supply alone is not enough to support overburdened sexual health services, which aren’t being given the support they need to work on both monkeypox, HIV prevention and STIs.

“We’re hearing of waiting times climbing for the HIV prevention drug, PrEP, which is unacceptable.

“We’re calling on the government to increase support for sexual health clinics to ensure efforts to end HIV transmissions aren’t derailed as an effect of monkeypox. If action isn’t taken urgently, we will see more people diagnosed with HIV.”