By Sola Ogundipe

The deployment of a safe and effective Lassa vaccine across 15 nations in  West Africa might save 3,300 lives and up to $128 million in societal expenditures over 10 years, a peer-reviewed study,  published in Nature Medicine has established.

Results of the study conducted by the Universities of Oxford and Liverpool and the Liverpool School of Tropical Medicine, vaccination against Lassa Fever – a viral disease spread by rodents and contaminated food – would shield millions of people from contracting the illness and the expensive medical bills that could otherwise force them into poverty.

In the view of the CEO of the Coalition for Epidemic Preparedness Innovations, CEPI,  Richard Hatchett,  “Lassa fever is a serious public health problem in West Africa and is already threatened to spread to further regions as climate and environmental change increase epidemic risk.

“This study demonstrates the urgent need for a vaccine to protect people from this debilitating and sometimes deadly disease which we believe affects many more than those who are reported, due to limited access to diagnostics and healthcare.”

The Head of Division – Preparedness and Response at the West African Health Organisation, Dr Virgil Lokossou,  said, “Lassa fever continues to pose a serious public health threat in West Africa, severely impacting our lives, health and economic systems. This modelling study highlights the burden of Lassa fever and its significant socioeconomic consequences, underscoring the urgent need to accelerate vaccine research and development as part of the regional preparedness and response efforts.”

The research team, led by Senior Researcher David Smith, also assessed the impact of deploying a vaccine against a new Lassa-like virus with pandemic potential – a hypothetical disease they called Lassa X – within 100 days of its emergence.

This was to model the potential impact of the 100 Days Mission in the event of a future human outbreak of a Lassa-like viral disease.

The result suggests that a population-wide vaccination campaign against Lassa fever in West Africa could significantly reduce the disease’s impact. By vaccinating 40 percent of the population annually with a safe and 70 percent effective vaccine within 100 days of an outbreak, researchers estimate that over 5,500 lives could be saved and 33,000 hospitalisations prevented during two years.

The study aligns with the global 100 Days Mission, led by CEPI, to develop vaccines against emerging diseases rapidly. It estimates that Lassa fever currently causes an average of 23,700 hospitalisations and 3,900 deaths annually in West Africa, but the actual burden is likely higher due to underreporting.

Modeling revealed that preventative vaccination campaigns targeting endemic areas are far more effective than reactive strategies implemented in response to outbreaks. While the latter can reduce the health-economic burden, they are only about 10 percent as effective as population-wide approaches.

David Smith, Senior Researcher at Oxford Population Health’s Health Economics Research Centre and joint first author, said ‘To our knowledge, this is the first burden of disease study for Lassa fever as well as the first to project impacts of Lassa vaccination campaigns on population health and economies.

“One major potential benefit of present investment in Lassa vaccination development is increased readiness to rapidly develop and deploy vaccines against future Lassa variants with pandemic potential.’

Joanne Turner, research associate at the University of Liverpool and joint first author, said,’The Lassa vaccination campaigns included in our analysis were designed to reflect realistic assumptions about vaccine stockpile and administration, and as such included a constrained global vaccine stockpile  below 20 million doses annually) and limited allocation to districts not currently classified as endemic by WHO.

“Consequently, the impacts of our simulated Lassa vaccination campaigns were modest in countries other than Nigeria, Guinea, Liberia, and Sierra Leone.

Yet the data underlying our model suggest that there is likely already a significant burden of Lassa fever outside these countries.’

Déirdre Hollingsworth, Professor of Infectious Disease Epidemiology at the University of Oxford Big Data Institute, said ‘Lassa fever predominantly affects low-income populations in rural areas and is likely to be highly underreported due to poor health access in these areas. This analysis highlights the potential impact of a vaccine in these populations.

Lassa fever has been identified by the World Health Organisation as one of the pathogens most likely to cause future severe outbreaks. Climate change and other environmental and demographic factors are threatening to put as many as 700 million people at risk of developing Lassa fever in the future, underscoring the pandemic potential of the virus and the urgent need for effective vaccines.

Symptoms include fever, headache, muscle pain and vomiting. In severe cases, victims suffer facial swelling and bleeding from the mouth, nose, vagina or gastrointestinal tract. About a quarter of those who survive severe Lassa fever infection develop deafness.

CEPI is one of the world’s leading Lassa vaccine R&D funders, investing in six potential vaccine candidates to date, of which four have progressed into human testing. One of CEPI’s partners, IAVI, has launched the first-ever Phase II clinical trial of a Lassa vaccine in Abuja, Nigeria.

Working with investigators in Nigeria, Benin, Guinea, Liberia, and Sierra Leone, CEPI is also conducting the largest-ever multi-country investigation of the epidemiology of Lassa to improve knowledge about the virus and how to counter its attacks.