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expert reaction to third confirmed case of Lassa fever in the UK, including one death

The UK Health Security Agency (UKHSA) have confirmed 3 cases Lassa fever following travel to West Africa, one of whom has died.


Dr Michael Head, Senior Research Fellow in Global Health, University of Southampton, said:

 “Lassa fever is a serious infection, but is nothing like as infectious as COVID-19.  Previous studies have estimated the R number of Lassa to be roughly between 1.0 and 1.6.

“The original wildtype coronavirus at the start of this pandemic had an R number of about 3, and the variants have become increasingly infectious. With the reported death, of course any Lassa cases within the UK are of concern. However, we won’t be seeing transmission anything like the scale we have with the COVID-19 pandemic, and the risks to the wider public are very low.

“The reporting has so far suggested the cases have a recent travel history from West Africa. There is an ongoing outbreak in Nigeria at the moment, with 911 suspected cases, 211 confirmed cases, and 40 deaths.”

Reproduction number of Lassa –

Nigeria outbreak –


Dr Melanie Saville, CEPI’s Director of Vaccine R&D, said:

“The three confirmed cases of the potentially deadly Lassa fever in the UK, now very sadly including one death, are a stark reminder of our interconnected world and the need to continue invest in outbreak preparedness and response efforts. Emerging infectious diseases are increasing in prevalence, severity, and spread as a result of climate change, global transportation, and human encroachment into previously isolated areas.

“Given the urgent need for vaccines, Lassa fever has remained one of our priority targets since CEPI first launched in 2017. With our partners in West Africa and across the world, we are advancing the development of six Lassa fever vaccines. Three of these—developed by Inovio Pharmaceuticals, IAVI, and Themis Bioscience—are the first in the world to enter clinical trials. CEPI’s ultimate goal, as part of our $3.5bn pandemic preparedness plan, is to produce a licensed Lassa vaccine for routine immunisation.

“To support the development of these vaccines, CEPI has created and funded the largest ever Lassa fever study, named Enable, to provide a more accurate assessment of the incidence of Lassa fever infections in the West African region. Over 20,000 participants are being recruited to take part in the study. The research will provide key information to help guide future late-stage Lassa vaccine clinical trials and potential vaccination strategies following licensure of a product.

“Finally, it is important to remember that Lassa virus is just one of a number of viruses within the Arenaviridae viral family. Recognising that other novel viruses within this family could emerge in the future with greater transmissibility and/or fatality rates, CEPI is using its Lassa vaccine work to guide the creation of a prototypic vaccine for use against the Arenaviridae family. The idea here is that this prototype vaccine could be ready to be pulled off the shelf and swiftly adapted next time a novel Arenaviridae virus emerges. That way, we don’t lose valuable time creating a new vaccine from scratch, helping to reach CEPI’s ambitious goal to develop future vaccines within 100 days.”



Declared interests

None received.

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