Monkeypox: Fractional vaccine doses will be piloted as new treatment trial launches
BMJ 2022; 378 doi: https://doi.org/10.1136/bmj.o2080 (Published 23 August 2022) Cite this as: BMJ 2022;378:o2080
Smaller doses of the smallpox vaccine, used to provide protection against monkeypox, will be piloted at NHS sites in London and Manchester to maximise supply, the UK Health Security Agency (UKHSA) has announced.
In the pilot scheme—which will take place at Chelsea and Westminster NHS Foundation Trust, Central and North West London NHS Foundation Trust, and Locala Health and Wellbeing in Greater Manchester—eligible adults will be offered a 0.1 mL dose of the smallpox Imvanex vaccine, instead of the 0.5 mL dose typically administered.
“Global supplies of the smallpox vaccine used to combat monkeypox are limited,” said UKHSA’s head of immunisation, Mary Ramsay. “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.”
Known as fractional dosing, the approach has also been authorised in the US by the Food and Drug Administration earlier this month1 and by the European Medicines Agency’s Emergency Task Force.2 In the US, STAT News has reported on some practical difficulties in extracting five doses from each vial.3
Evidence base
The UKHSA has said that the approach provides a “near-identical immune response in patients,” highlighting a US study published in Vaccine as evidence. The study included just over 500 people and reported that the lower dose of attenuated smallpox vaccine (sold as Imvanex in the EU and the UK and as Jynneos in the US) was “immunologically non-inferior to the standard subcutaneous dose.”4
Both the UKHSA and the Joint Committee on Vaccination and Immunisation have reviewed the available evidence and recommended the fractional dosing approach. Results from the pilot scheme will be used to inform planning for possible wider use when more doses of the vaccine arrive in the UK, the agency has said.
Commenting on the announcement, Will Nutland, who cofounded the HIV prevention campaign group PrEPster and is an honorary assistant professor at the London School of Hygiene and Tropical Medicine, 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.”
The UKHSA has also said that, because of the limited vaccine supply, the post-exposure offer of vaccination will now be reserved for those close contacts with the highest risk of severe illness, such as people with immunosuppression, children under 5, and pregnant women. These people will be given a standard dose.
New treatments
In other monkeypox news, the lead researchers behind the covid-19 Recovery trial are launching a new trial investigating a potential treatment for people with a monkeypox diagnosis.
The Placebo-Controlled Randomised Trial of Tecovirimat in Non-Hospitalised Monkeypox Patients (Platinum), commissioned and funded by the National Institute for Health and Care Research, has already recruited its first patients and will start by testing the efficacy and safety of antiviral tecovirimat—originally developed for smallpox.
Tecovirimat is already being used to treat patients admitted to hospital with severe complications of monkeypox, but there have been no clinical trials to confirm its effectiveness in this patient group.
Although monkeypox usually gets better without treatment, this can take several weeks, and in rare cases it can cause serious complications. Currently, there are no proven therapeutics to speed recovery in people who develop the disease.
The Platinum trial is being led by Peter Horby, professor of emerging infections and global health at the University of Oxford, and Martin Landray, professor of medicine and epidemiology at Oxford Population Health.
The community based trial will recruit at least 500 participants from around the UK, who will receive either a 14 day course of 600 mg tecovirimat twice daily or a matched placebo treatment. The researchers will be looking to see whether the drug increases the rate at which skin and mucosal lesions heal, whether it reduces the time for throat and lesion swabs to test negative for the monkeypox virus, and whether it cuts the proportion of patients requiring hospital admission.
Footnotes
bmj.com News briefing—Monkeypox: what we know about the 2022 outbreak so far (BMJ 2022;378:o2058, doi:10.1136/bmj.o2058)