A NEW study has projected that the deployment of a Lassa fever vaccine across 15 West African countries could save 3,300 lives and prevent societal costs amounting to $128 million over the next decade.
The research, conducted by the Nigeria Centre for Disease Control, NCDC, alongside experts from Oxford and Liverpool Universities, and the Liverpool School of Tropical Medicine and published by Nature Medicine on August 28, 2024, noted the urgent need for a Lassa fever vaccine to prevent the ongoing spread of the viral disease.
Lassa fever is a deadly viral hemorrhagic illness that lowers the platelet count in the blood and its ability to clot, causing internal bleeding.
It is primarily transmitted to humans via contact with food or household items contaminated with urine or faeces from Mastomys rats.
Though to a lesser extent, secondary human-to-human transmission can also occur through direct contact with infected persons’ blood, secretions, organs, or other body fluids, especially in health-care settings could also transmit, according to the World Health Organization (WHO).
The report also highlighted the impact of Lassa fever on healthcare costs, with thousands of people being hospitalised each year.
The modelling, which predicted approximately 2.7 million Lassa virus infections yearly, indicated that a population-wide vaccination campaign targeting endemic areas could avert 19,000 hospitalisations, 3,300 deaths, and 164,100 disability-adjusted life years (DALYs).
“For a vaccine, 70 per cent effective against disease with no impact on infection, over 10 years this strategy averted a mean 456, 000 (226,400–822,700) mild/moderate symptomatic cases, 19,900 (12,700–28,800) hospitalisations, 3,300 (1,100–7,000) deaths and 164,100 (66,700–317,700) DALYs.
“Over this period, this strategy further prevented 19,800 (12,600–28,500) and 14,200 (9,000–20,500) individuals, respectively, from experiencing catastrophic or impoverishing out-of-pocket healthcare expenditures and averted $128.2 million ($67.2–$231.9 million) in societal costs, or $1.3 billion ($436.8 million–$2.8 billion) in VSL lost,” the report stated.
This strategy, according to the study, would also prevent catastrophic healthcare expenditures for over 14,000 individuals and save $128.2 million in societal costs.
The most effective vaccination strategy was a population-wide preventive campaign primarily targeting WHO-classified ‘endemic’ districts.
In contrast, reactive vaccination campaigns responding to local outbreaks were found to avert only one-tenth of the health-economic burden compared to the large-scale preventative approach.
Potential impact of Lassa fever vaccine
A vaccination campaign could significantly reduce Lassa fever’s health and economic burden, especially in endemic areas, according to Virgil Lokossou, a doctor and head of division, Preparedness and Response at the West African Health Organisation.
“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 West African Health Organisation remains committed to working with our Member States, CEPI, and all stakeholders to ensure that we fast-track the development of a vaccine and other tools we need to control the spread of Lassa fever and protect our communities. Time is now up for concrete actions,” Lokossou said.
The study also examined the potential for a Lassa-like virus, termed “Lassa-X,” with pandemic potential, adding that if Lassa-X were to emerge, causing rapid human-to-human transmission, about 25,000 deaths and 1.2 million DALYs were projected over two years.
In the event of an outbreak, administering a safe and effective Lassa X vaccine within 100 days to 40 percent of people per year could prevent 33,000 hospitalizations and save 5,500 lives during a two-year pandemic scenario.
The WHO has recognised Lassa fever as one of the pathogens most likely to cause future severe outbreaks.
The WHO notes that despite increased capacity for preventing and controlling Lassa fever, including enhanced surveillance, diagnostic, and treatment capabilities, several factors continue to elevate the risk.
These factors include a rise in confirmed cases, climate change, surveillance gaps, inconsistent subnational response capacities, delays in sample shipments for laboratory testing, and chronic underfunding.
On the effectiveness, the study found that a widespread, preventative vaccination strategy would be far more effective than reactive campaigns in response to outbreaks.
Richard Hatchett, CEO of Coalition for Epidemic Preparedness Innovations, CEPI, emphasised the growing risk of Lassa fever due to climate change and limited healthcare access.
“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 affect many more than those who are reported, due to limited access to diagnostics and healthcare. Lassa fever has been a priority for CEPI since our launch in 2017 and we are proud to be one of the world’s leading Lassa vaccine R&D funders.”
Socio-economic benefit
The study’s economic modelling further noted that vaccination would reduce catastrophic healthcare expenditures for individuals and prevent many from falling below the poverty line due to out-of-pocket healthcare costs.
According to the report, a large-scale, preventive vaccination campaign targeting WHO-classified endemic districts would require 112 million doses over 10 years.
This would avert 20,000–29,000 hospitaliasations, 3,300–4,800 deaths, and 164,000–240,000 DALYs.
The financial benefit would be between $42–$61 million in healthcare savings and $86–$126 million in productivity losses, translating into $1.3–$1.9 billion in societal benefits in total.
Meanwhile, Virgil Lokossou, called for faster vaccine development to mitigate the disease’s devastating health and economic consequences in the region.
He noted that Lassa fever continues to impact public health and disrupt economic systems in West Africa, and urgent action is needed to control the disease.
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.”
Usman Mustapha is a solution journalist with International Centre for Investigative Reporting. You can easily reach him via: [email protected]. He tweets @UsmanMustapha_M