In the pilot – 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 0.1ml dose of the vaccine against smallpox Imvanex. instead of the 0.5 mL dose usually given. “Global supplies of the smallpox vaccine used to fight smallpox are limited,” UKHSA head of vaccination Mary Ramsay said. “Adopting this proven technique will help maximize the reach of our remaining stockpile, including the 100,000 doses due to arrive in the country next month, potentially allowing us to offer protection to many thousands more people.” Known as fractional dosing, the approach has also been approved in the US by the Food and Drug Administration earlier this month1 and by the European Medicines Agency’s Emergency Response Team.2 In the US, STAT News reported some practical difficulties in extracting five doses from each vial.3
Evidence base
The UKHSA said the approach provides an “almost identical immune response in patients”, pointing to a US study published in Vaccine as evidence. The study involved just over 500 people and said the lower dose of the attenuated smallpox vaccine (sold as Imvanex in the EU and UK and as Jynneos in the US) was “immunologically non-inferior to the standard subcutaneous dose”. Both the UKHSA and the Joint Committee on Vaccination and Immunization reviewed the available evidence and recommended the fractional dosing approach. Results from the pilot program will be used to inform planning for possible wider use when more doses of the vaccine arrive in the UK, the agency said. Commenting on the announcement, Will Nutland, who founded the HIV prevention campaign group PrEPster and is an honorary assistant professor at the London School of Hygiene and Tropical Medicine, said: “The evidence shows that fractional dosing, when given correctly, is just as effective with the currently used vaccination method. We must now act collectively to ensure that those who are given the opportunity to be vaccinated are fully informed and confident that they will turn up when invited.” The UKHSA also said that, due to limited vaccine supply, the post-exposure vaccination offer will now be reserved for those close contacts at highest risk of serious illness, such as immunosuppressed people, 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 diagnosed with monkeypox. The placebo-controlled randomized trial of Tecovirimat in outpatients with monkeypox (Platinum), commissioned and funded by the National Institute for Health and Care Research, has already recruited its first patients and will begin by testing its efficacy and safety antiviral tecovirimat— originally developed for smallpox. Tecovirimat is already used to treat patients admitted to hospital with severe complications of monkeypox, but no clinical trials have been carried out to confirm its effectiveness in this group of patients. Although monkeypox usually gets better without treatment, this can take several weeks and in rare cases can cause serious complications. Currently, there are no proven treatments 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 trial will recruit at least 500 participants from across the UK, who will receive either a 14-day regimen of 600 mg tecovirimat twice daily or a matching placebo treatment. The researchers will look to see if the drug increases the rate at which skin and mucosal lesions heal, if it reduces the time for throat swabs and lesions to test negative for monkeypox virus, and if it reduces the proportion of patients requiring hospital admission. .
Footnotes
bmj.com news update—Monkeypox: what we know about the 2022 outbreak so far (BMJ 2022;378:o2058, doi:10.1136/bmj.o2058)
