Journal Article > ResearchFull Text
J Trop Med. 3 November 2024; Online ahead of print; DOI:10.1111/tmi.14053
Melingui BF, Basant J, Taguebue Jv, Massom DM, Leroy Terquem E, et al.
J Trop Med. 3 November 2024; Online ahead of print; DOI:10.1111/tmi.14053
OBJECTIVES
Chest x‐ray (CXR) plays an important role in childhood tuberculosis (TB) diagnosis, but access to quality CXR remains a major challenge in resource‐limited settings. Digital CXR (d‐CXR) can solve some image quality issues and facilitate their transfer for quality control. We assess the implementation of introducing d‐CXR in 12 district hospitals (DHs) in 2021–2022 across Cambodia, Cameroon, Ivory Coast, Mozambique, Sierra Leone and Uganda as part of the TB‐speed decentralisation study on childhood TB diagnosis.
METHODS
For digitisation of CXR, digital radiography (DR) plates were setup on existing analogue radiography devices. d‐CXR were transferred to an international server at Bordeaux University and downloaded by sites' clinicians for interpretation. We assessed the uptake and performance of CXR services and health care workers' (HCW) perceptions of d‐CXR implementation. We used a convergent mixed method approach utilising process data, individual interviews with 113 HCWs involved in performing or interpreting d‐CXRs and site support supervision reports.
RESULTS
Of 3104 children with presumptive TB, 1642 (52.9%) had at least one d‐CXR, including 1505, 136 and 1 children with one, two and three d‐CXRs, respectively, resulting in a total of 1780 d‐CXR. Of them, 1773 (99.6%) were of good quality and 1772/1773 (99.9%) were interpreted by sites' clinicians. One hundred and sixty‐four children had no d‐CXR performed despite attending the radiography department: 126, 37 and 1 with one, two and three attempts, respectively. d‐CXRs were not performed in 21.6% (44/203) due to connectivity problem between the DR plate captor and the computer. HCW reported good perceptions of d‐CXR and of the DR plates provided. The main challenge was the upload to and download from the server of d‐CXRs due to limited internet access.
CONCLUSION
d‐CXR using DR plates was feasible at DH level and provided good quality images but required overcoming operational challenges.
Conference Material > Poster
Keshk M, Vala L, Gana J, Coneh M, Obeidat A, et al.
MSF Paediatric Days 2024. 3 May 2024; DOI:10.57740/ZcSSAg
Journal Article > ResearchFull Text
Glob Health Action. 25 April 2024; Volume 17 (Issue 1); 2331291.; DOI:10.1080/16549716.2024.2331291
Caleo G, Lokuge K, Kardamanidis K, Greig J, Belava J, et al.
Glob Health Action. 25 April 2024; Volume 17 (Issue 1); 2331291.; DOI:10.1080/16549716.2024.2331291
BACKGROUND
There is a lack of empirical data on design effects (DEFF) for mortality rate for highly clustered data such as with Ebola virus disease (EVD), along with a lack of documentation of methodological limitations and operational utility of mortality estimated from cluster-sampled studies when the DEFF is high.
OBJECTIVES
The objectives of this paper are to report EVD mortality rate and DEFF estimates, and discuss the methodological limitations of cluster surveys when data are highly clustered such as during an EVD outbreak.
METHODS
We analysed the outputs of two independent population-based surveys conducted at the end of the 2014-2016 EVD outbreak in Bo District, Sierra Leone, in urban and rural areas. In each area, 35 clusters of 14 households were selected with probability proportional to population size. We collected information on morbidity, mortality and changes in household composition during the recall period (May 2014 to April 2015). Rates were calculated for all-cause, all-age, under-5 and EVD-specific mortality, respectively, by areas and overall. Crude and adjusted mortality rates were estimated using Poisson regression, accounting for the surveys sample weights and the clustered design.
RESULTS
Overall 980 households and 6,522 individuals participated in both surveys. A total of 64 deaths were reported, of which 20 were attributed to EVD. The crude and EVD-specific mortality rates were 0.35/10,000 person-days (95%CI: 0.23-0.52) and 0.12/10,000 person-days (95%CI: 0.05-0.32), respectively. The DEFF for EVD mortality was 5.53, and for non-EVD mortality, it was 1.53. DEFF for EVD-specific mortality was 6.18 in the rural area and 0.58 in the urban area. DEFF for non-EVD-specific mortality was 1.87 in the rural area and 0.44 in the urban area.
CONCLUSION
Our findings demonstrate a high degree of clustering; this contributed to imprecise mortality estimates, which have limited utility when assessing the impact of disease. We provide DEFF estimates that can inform future cluster surveys and discuss design improvements to mitigate the limitations of surveys for highly clustered data.
There is a lack of empirical data on design effects (DEFF) for mortality rate for highly clustered data such as with Ebola virus disease (EVD), along with a lack of documentation of methodological limitations and operational utility of mortality estimated from cluster-sampled studies when the DEFF is high.
OBJECTIVES
The objectives of this paper are to report EVD mortality rate and DEFF estimates, and discuss the methodological limitations of cluster surveys when data are highly clustered such as during an EVD outbreak.
METHODS
We analysed the outputs of two independent population-based surveys conducted at the end of the 2014-2016 EVD outbreak in Bo District, Sierra Leone, in urban and rural areas. In each area, 35 clusters of 14 households were selected with probability proportional to population size. We collected information on morbidity, mortality and changes in household composition during the recall period (May 2014 to April 2015). Rates were calculated for all-cause, all-age, under-5 and EVD-specific mortality, respectively, by areas and overall. Crude and adjusted mortality rates were estimated using Poisson regression, accounting for the surveys sample weights and the clustered design.
RESULTS
Overall 980 households and 6,522 individuals participated in both surveys. A total of 64 deaths were reported, of which 20 were attributed to EVD. The crude and EVD-specific mortality rates were 0.35/10,000 person-days (95%CI: 0.23-0.52) and 0.12/10,000 person-days (95%CI: 0.05-0.32), respectively. The DEFF for EVD mortality was 5.53, and for non-EVD mortality, it was 1.53. DEFF for EVD-specific mortality was 6.18 in the rural area and 0.58 in the urban area. DEFF for non-EVD-specific mortality was 1.87 in the rural area and 0.44 in the urban area.
CONCLUSION
Our findings demonstrate a high degree of clustering; this contributed to imprecise mortality estimates, which have limited utility when assessing the impact of disease. We provide DEFF estimates that can inform future cluster surveys and discuss design improvements to mitigate the limitations of surveys for highly clustered data.
Journal Article > ResearchFull Text
E Clinical Medicine. 21 March 2024; Volume 70; 102528.; DOI:10.1016/j.eclinm.2024.102528
d’Elbée M, Harker M, Mafirakureva N, Nanfuka M, Nguyet MHTN, et al.
E Clinical Medicine. 21 March 2024; Volume 70; 102528.; DOI:10.1016/j.eclinm.2024.102528
Journal Article > ResearchFull Text
ACG Case Rep J. 21 March 2024; Volume 70; 102527.; DOI:10.1016/j.eclinm.2024.102527
Wobudeya E, Nanfuka M, Ton Nu Nguyet MH, Taguebue JV, Moh R, et al.
ACG Case Rep J. 21 March 2024; Volume 70; 102527.; DOI:10.1016/j.eclinm.2024.102527
BACKGROUND
Childhood tuberculosis (TB) remains underdiagnosed largely because of limited awareness and poor access to all or any of specimen collection, molecular testing, clinical evaluation, and chest radiography at low levels of care. Decentralising childhood TB diagnostics to district hospitals (DH) and primary health centres (PHC) could improve case detection.
METHODS
We conducted an operational research study using a pre-post intervention cross-sectional study design in 12 DHs and 47 PHCs of 12 districts across Cambodia, Cameroon, Côte d'Ivoire, Mozambique, Sierra Leone and Uganda. The intervention included 1) a comprehensive diagnosis package at patient-level with tuberculosis screening for all sick children and young adolescents <15 years, and clinical evaluation, Xpert Ultra-testing on respiratory and stool samples, and chest radiography for children with presumptive TB, and 2) two decentralisation approaches (PHC-focused or DH-focused) to which districts were randomly allocated at country level. We collected aggregated and individual data. We compared the proportion of tuberculosis detection in children and young adolescents <15 years pre-intervention (01 August 2018-30 November 2019) versus during intervention (07 March 2020-30 September 2021), overall and by decentralisation approach. This study is registered with ClinicalTrials.gov, NCT04038632.
FINDINGS
TB was diagnosed in 217/255,512 (0.08%) children and young adolescent <15 years attending care pre-intervention versus 411/179,581 (0.23%) during intervention, (OR: 3.59 [95% CI 1.99-6.46], p-value<0.0001; p-value = 0.055 after correcting for over-dispersion). In DH-focused districts, TB diagnosis was 80/122,570 (0.07%) versus 302/86,186 (0.35%) (OR: 4.07 [1.86-8.90]; p-value = 0.0005; p-value = 0.12 after correcting for over-dispersion); and 137/132,942 (0.10%) versus 109/93,395 (0.11%) in PHC-focused districts, respectively (OR: 2.92 [1.25-6.81; p-value = 0.013; p-value = 0.26 after correcting for over-dispersion).
INTERPRETATION
Decentralising and strengthening childhood TB diagnosis at lower levels of care increases tuberculosis case detection but the difference was not statistically significant.
Childhood tuberculosis (TB) remains underdiagnosed largely because of limited awareness and poor access to all or any of specimen collection, molecular testing, clinical evaluation, and chest radiography at low levels of care. Decentralising childhood TB diagnostics to district hospitals (DH) and primary health centres (PHC) could improve case detection.
METHODS
We conducted an operational research study using a pre-post intervention cross-sectional study design in 12 DHs and 47 PHCs of 12 districts across Cambodia, Cameroon, Côte d'Ivoire, Mozambique, Sierra Leone and Uganda. The intervention included 1) a comprehensive diagnosis package at patient-level with tuberculosis screening for all sick children and young adolescents <15 years, and clinical evaluation, Xpert Ultra-testing on respiratory and stool samples, and chest radiography for children with presumptive TB, and 2) two decentralisation approaches (PHC-focused or DH-focused) to which districts were randomly allocated at country level. We collected aggregated and individual data. We compared the proportion of tuberculosis detection in children and young adolescents <15 years pre-intervention (01 August 2018-30 November 2019) versus during intervention (07 March 2020-30 September 2021), overall and by decentralisation approach. This study is registered with ClinicalTrials.gov, NCT04038632.
FINDINGS
TB was diagnosed in 217/255,512 (0.08%) children and young adolescent <15 years attending care pre-intervention versus 411/179,581 (0.23%) during intervention, (OR: 3.59 [95% CI 1.99-6.46], p-value<0.0001; p-value = 0.055 after correcting for over-dispersion). In DH-focused districts, TB diagnosis was 80/122,570 (0.07%) versus 302/86,186 (0.35%) (OR: 4.07 [1.86-8.90]; p-value = 0.0005; p-value = 0.12 after correcting for over-dispersion); and 137/132,942 (0.10%) versus 109/93,395 (0.11%) in PHC-focused districts, respectively (OR: 2.92 [1.25-6.81; p-value = 0.013; p-value = 0.26 after correcting for over-dispersion).
INTERPRETATION
Decentralising and strengthening childhood TB diagnosis at lower levels of care increases tuberculosis case detection but the difference was not statistically significant.
Journal Article > ResearchFull Text
IJTLD OPEN. 1 February 2024; Volume 1 (Issue 2); 76-82.; DOI:10.5588/ijtldopen.23.0484
Melingui BF, Leroy-Terquem E, Palmer M, Taguebue JV, Wachinou AP, et al.
IJTLD OPEN. 1 February 2024; Volume 1 (Issue 2); 76-82.; DOI:10.5588/ijtldopen.23.0484
BACKGROUND
Chest X-ray (CXR) interpretation is challenging for the diagnosis of paediatric TB. We assessed the performance of a three half-day CXR training module for healthcare workers (HCWs) at low healthcare levels in six high TB incidence countries.
METHODS
Within the TB-Speed Decentralization Study, we developed a three half-day training course to identify normal CXR, CXR of good quality and identify six TB-suggestive features. We performed a pre–post training assessment on a pre-defined set of 20 CXR readings. We compared the proportion of correctly interpreted CXRs and the median reading score before and after the training using the McNemar test and a linear mixed model.
RESULTS
Of 191 HCWs, 43 (23%) were physicians, 103 (54%) nurses, 18 (9.4%) radiology technicians and 12 (6.3%) other professionals. Of 2,840 CXRs with both assessment, respectively 1,843 (64.9%) and 2,277 (80.2%) were correctly interpreted during pre-training and post-training (P < 0.001). The median reading score improved significantly from 13/20 to 16/20 after the training, after adjusting by country, facility and profession (adjusted β = 3.31, 95% CI 2.44–4.47).
CONCLUSION
Despite some limitations of the course assessment that did not include abnormal non-TB suggestive CXR, study findings suggest that a short CXR training course could improve HCWs’ interpretation skills in diagnosing paediatric TB.
Chest X-ray (CXR) interpretation is challenging for the diagnosis of paediatric TB. We assessed the performance of a three half-day CXR training module for healthcare workers (HCWs) at low healthcare levels in six high TB incidence countries.
METHODS
Within the TB-Speed Decentralization Study, we developed a three half-day training course to identify normal CXR, CXR of good quality and identify six TB-suggestive features. We performed a pre–post training assessment on a pre-defined set of 20 CXR readings. We compared the proportion of correctly interpreted CXRs and the median reading score before and after the training using the McNemar test and a linear mixed model.
RESULTS
Of 191 HCWs, 43 (23%) were physicians, 103 (54%) nurses, 18 (9.4%) radiology technicians and 12 (6.3%) other professionals. Of 2,840 CXRs with both assessment, respectively 1,843 (64.9%) and 2,277 (80.2%) were correctly interpreted during pre-training and post-training (P < 0.001). The median reading score improved significantly from 13/20 to 16/20 after the training, after adjusting by country, facility and profession (adjusted β = 3.31, 95% CI 2.44–4.47).
CONCLUSION
Despite some limitations of the course assessment that did not include abnormal non-TB suggestive CXR, study findings suggest that a short CXR training course could improve HCWs’ interpretation skills in diagnosing paediatric TB.
Journal Article > CommentaryFull Text
Journal of Humanitarian Affairs. 23 November 2023; Volume 5 (Issue 2); 24-29.; DOI:10.7227/JHA.107
Leyland J, Tiller S, Bhattacharya B
Journal of Humanitarian Affairs. 23 November 2023; Volume 5 (Issue 2); 24-29.; DOI:10.7227/JHA.107
While health misinformation is important to address in humanitarian settings, over-focusing on it can obfuscate a more holistic understanding of a community’s needs in a crisis. Through Médecins Sans Frontières’ experience of deploying a platform to tackle health misinformation during the COVID-19 pandemic, this field report argues that, while important, health misinformation became a diversionary topic during COVID-19, which represented a lack of trust between communities, humanitarian organisations and health institutions, rather a fundamental obstacle to effective humanitarian interventions.
From our practitioners’ viewpoint, we reflect on the deployment of the ‘MSF Listen’ platform in our programmes and how it evolved from a purely misinformation-focused digital tool to a broader workflow and approach to understanding community needs in crises through accountable management of community feedback.
From our practitioners’ viewpoint, we reflect on the deployment of the ‘MSF Listen’ platform in our programmes and how it evolved from a purely misinformation-focused digital tool to a broader workflow and approach to understanding community needs in crises through accountable management of community feedback.
Journal Article > ResearchFull Text
PLOS Glob Public Health. 11 October 2023; Volume 3 (Issue 10); e0001525.; DOI:10.1371/journal.pgph.0001525
Joshi B, De Lima YV, Massom DM, Kaing S, Banga MF, et al.
PLOS Glob Public Health. 11 October 2023; Volume 3 (Issue 10); e0001525.; DOI:10.1371/journal.pgph.0001525
Decentralizing childhood tuberculosis services, including diagnosis, is now recommended by the WHO and could contribute to increasing tuberculosis detection in high burden countries. However, implementing microbiological tests and clinical evaluation could be challenging for health care workers (HCWs) in Primary Health Centers (PHCs) and even District Hospitals (DHs). We sought to assess the acceptability of decentralizing a comprehensive childhood tuberculosis diagnosis package from HCWs’ perspective. We conducted implementation research nested within the TB-Speed Decentralization study. HCWs from two health districts of Cambodia, Cameroon, Côte d’Ivoire, Mozambique, Sierra Leone, and Uganda implemented systematic screening, nasopharyngeal aspirates (NPA) and stool sample collection with molecular testing, clinical evaluation and chest X-ray (CXR) interpretation. We investigated their experiences and perceptions in delivering the diagnostic package components in 2020–21 using individual semi-structured interviews. We conducted thematic analysis, supported by the Theoretical Framework of Acceptability. HCWs (n = 130, 55% female, median age 36 years, 53% nurses, 72% PHC-based) perceived that systematic screening, although increasing workload, was beneficial as it improved childhood tuberculosis awareness. Most HCWs shared satisfaction and confidence in performing NPA, despite procedure duration, need to involve parents/colleagues and discomfort for children. HCWs shared positive attitudes towards stool sample-collection but were frustrated by delayed stool collection associated with cultural practices, transport and distance challenges. Molecular testing, conducted by nurses or laboratory technicians, was perceived as providing quality results, contributing to diagnosis. Clinical evaluation and diagnosis raised self-efficacy issues and need for continuous training and clinical mentoring. HCWs valued CXR, however complained that technical and logistical problems limited access to digital reports. Referral from PHC to DH was experienced as burdensome. HCWs at DH and PHC-levels perceived and experienced decentralized childhood tuberculosis diagnosis as acceptable. Implementation however could be hampered by feasibility issues, and calls for innovative referral mechanisms for patients, samples and CXR.
Conference Material > Abstract
Natukunda N
Epicentre Scientific Day 2023. 8 June 2023
BACKGROUND
Childhood tuberculosis is underdiagnosed at low-level healthcare settings because of poor access to specimen collection, rapid molecular testing, clinical evaluation and chest radiography. Decentralizing childhood tuberculosis diagnosis at district hospital (DH) and primary health centre (PHC) levels could improve case detection.
METHODS
TB-Speed decentralisation is an operational research using a pre-post intervention cross-sectional design in 12 DHs and 47 PHCs of 12 districts in Cambodia, Cameroon, Côte d’Ivoire, Mozambique, Sierra Leone and Uganda. The intervention included a comprehensive childhood tuberculosis diagnosis package consisting of systematic tuberculosis screening for all under-15-year-old sick children, clinical evaluation, Xpert Ultra-testing on one nasopharyngeal aspirate (NPA) and stool samples, and chest radiography for children with presumptive tuberculosis, using either PHC-focused or DH-focused decentralization approaches. We collected aggregated and individual data for children whose parents consented. We present the comparison of the proportion of tuberculosis case detected pre-intervention from August 2018 to Nov 2019 versus post-intervention from March 2020 to September 2021, overall and by decentralization approach, and the uptake and acceptability of the diagnostic package in Uganda.
FINDINGS
In Uganda, 52233 and 46035 children attended care pre-intervention versus post-intervention respectively. 26/52233 (0.05%) and 42/46035 (0.09%) children were diagnosed with tuberculosis pre-intervention and post-intervention respectively, p-value=0.114. In DH-focused district, it was 10/24208 (0.04%) and 23/17914 (0.1%) pre-intervention and post-intervention respectively, and 16/28025 (0.06%) and 19/28121 (0.1%) for PHC-districts, respectively. The uptake of TB screening was 43104/46035 (93.6%) overall, among the 732 enrolled children 724/ and 532 had a valid Ultra result using NPA and stool, respectively. Health care workers overall experienced decentralized childhood TB diagnostic as acceptable, with NPA and stool sample collection feasible both at DH and PHC.
CONCLUSION
Decentralizing innovative childhood tuberculosis diagnosis can increase tuberculosis case detection with limited impact when using the PHC decentralization approach.
KEY MESSAGE
Although decentralizing childhood TB diagnosis is acceptable, overcoming feasibility issues may improve the effective implementation and scale-up of such interventions at low levels of care.
This abstract is not to be quoted for publication.
Childhood tuberculosis is underdiagnosed at low-level healthcare settings because of poor access to specimen collection, rapid molecular testing, clinical evaluation and chest radiography. Decentralizing childhood tuberculosis diagnosis at district hospital (DH) and primary health centre (PHC) levels could improve case detection.
METHODS
TB-Speed decentralisation is an operational research using a pre-post intervention cross-sectional design in 12 DHs and 47 PHCs of 12 districts in Cambodia, Cameroon, Côte d’Ivoire, Mozambique, Sierra Leone and Uganda. The intervention included a comprehensive childhood tuberculosis diagnosis package consisting of systematic tuberculosis screening for all under-15-year-old sick children, clinical evaluation, Xpert Ultra-testing on one nasopharyngeal aspirate (NPA) and stool samples, and chest radiography for children with presumptive tuberculosis, using either PHC-focused or DH-focused decentralization approaches. We collected aggregated and individual data for children whose parents consented. We present the comparison of the proportion of tuberculosis case detected pre-intervention from August 2018 to Nov 2019 versus post-intervention from March 2020 to September 2021, overall and by decentralization approach, and the uptake and acceptability of the diagnostic package in Uganda.
FINDINGS
In Uganda, 52233 and 46035 children attended care pre-intervention versus post-intervention respectively. 26/52233 (0.05%) and 42/46035 (0.09%) children were diagnosed with tuberculosis pre-intervention and post-intervention respectively, p-value=0.114. In DH-focused district, it was 10/24208 (0.04%) and 23/17914 (0.1%) pre-intervention and post-intervention respectively, and 16/28025 (0.06%) and 19/28121 (0.1%) for PHC-districts, respectively. The uptake of TB screening was 43104/46035 (93.6%) overall, among the 732 enrolled children 724/ and 532 had a valid Ultra result using NPA and stool, respectively. Health care workers overall experienced decentralized childhood TB diagnostic as acceptable, with NPA and stool sample collection feasible both at DH and PHC.
CONCLUSION
Decentralizing innovative childhood tuberculosis diagnosis can increase tuberculosis case detection with limited impact when using the PHC decentralization approach.
KEY MESSAGE
Although decentralizing childhood TB diagnosis is acceptable, overcoming feasibility issues may improve the effective implementation and scale-up of such interventions at low levels of care.
This abstract is not to be quoted for publication.
Conference Material > Abstract
Camacho A
Epicentre Scientific Day 2023. 8 June 2023
BACKGROUND
Lassa fever (LF), a haemorrhagic illness caused by the Lassa fever virus (LASV), is endemic in West Africa causing an estimated 300 000 to 500 000 cases and 5 000 fatalities every year. Due to its pandemic potential, LF has been placed on the WHO's list of priority pathogens in order to speed up the development of a safe and effective vaccine. However, the design of successful vaccine trials depends on the true prevalence and incidence rates of LF, which are unknown as infections are often asymptomatic and clinical presentations are varied. The aim of the Enable Lassa research programme is to estimate the incidences of LASV infection and LF disease in five West African countries.
METHODS
We conducted a prospective cohort study in Benin, Guinea, Liberia, Nigeria (three sites), and Sierra Leone from 2020 to 2023, with 24 months of follow-up. Each site assessed the incidence of LASV infection, LF disease, or both. When both incidences are assessed the LASV cohort (n = 1 000 per site) was drawn from the LF cohort (n = 5 000 per site). During recruitment participants completed questionnaires on household composition, socioeconomic status, demographic characteristics, and LF history, and blood samples were collected to determine IgG LASV serostatus. LF disease cohort participants were contacted biweekly to identify acute febrile cases, from whom blood samples were drawn to test for active LASV infection using RT-PCR. LASV infection cohort participants were asked for a blood sample every six months to assess LASV IgG serostatus.
RESULTS
Interim results were obtained in October 2022 using partial data. We focus here on the Nigeria-Edo cohort with a follow-up period of 22 months and 3 serological time-points available (T0, T6, T12). We found a baseline seroprevalence of 43% (95% CI: 42% - 45%), an incidence rate of LASV infection of 13% (10% - 16%) and an incidence rate of LF disease of 0.2% (0.1% - 0.3%). These results suggest that LASV infection is common, but LF disease is rare in hotspot communities. Furthermore, our results suggest that pre-exposure to LASV may temporarily reduce the risk of LF disease. Finally, we found evidence that children may be at greater risk of LF disease than adults due to lower pre-exposure.
CONCLUSION
This is the first epidemiological study to measure the incidence of LF disease and LASV infection in West Africa. The estimates will serve as a basis for the design of future vaccine efficacy trials. The interim results, although limited due to partial data, already suggest that a large sample of several tens of thousands of participants will be required and that children should be included, provided that the candidate vaccine is safe and immunogenic in this group.
KEY MESSAGE
Incidence of Lassa fever is needed to inform vaccine trials. Preliminary results show frequent infections but rare disease, suggesting the need for large vaccine trials.
This abstract is not to be quoted for publication.
Lassa fever (LF), a haemorrhagic illness caused by the Lassa fever virus (LASV), is endemic in West Africa causing an estimated 300 000 to 500 000 cases and 5 000 fatalities every year. Due to its pandemic potential, LF has been placed on the WHO's list of priority pathogens in order to speed up the development of a safe and effective vaccine. However, the design of successful vaccine trials depends on the true prevalence and incidence rates of LF, which are unknown as infections are often asymptomatic and clinical presentations are varied. The aim of the Enable Lassa research programme is to estimate the incidences of LASV infection and LF disease in five West African countries.
METHODS
We conducted a prospective cohort study in Benin, Guinea, Liberia, Nigeria (three sites), and Sierra Leone from 2020 to 2023, with 24 months of follow-up. Each site assessed the incidence of LASV infection, LF disease, or both. When both incidences are assessed the LASV cohort (n = 1 000 per site) was drawn from the LF cohort (n = 5 000 per site). During recruitment participants completed questionnaires on household composition, socioeconomic status, demographic characteristics, and LF history, and blood samples were collected to determine IgG LASV serostatus. LF disease cohort participants were contacted biweekly to identify acute febrile cases, from whom blood samples were drawn to test for active LASV infection using RT-PCR. LASV infection cohort participants were asked for a blood sample every six months to assess LASV IgG serostatus.
RESULTS
Interim results were obtained in October 2022 using partial data. We focus here on the Nigeria-Edo cohort with a follow-up period of 22 months and 3 serological time-points available (T0, T6, T12). We found a baseline seroprevalence of 43% (95% CI: 42% - 45%), an incidence rate of LASV infection of 13% (10% - 16%) and an incidence rate of LF disease of 0.2% (0.1% - 0.3%). These results suggest that LASV infection is common, but LF disease is rare in hotspot communities. Furthermore, our results suggest that pre-exposure to LASV may temporarily reduce the risk of LF disease. Finally, we found evidence that children may be at greater risk of LF disease than adults due to lower pre-exposure.
CONCLUSION
This is the first epidemiological study to measure the incidence of LF disease and LASV infection in West Africa. The estimates will serve as a basis for the design of future vaccine efficacy trials. The interim results, although limited due to partial data, already suggest that a large sample of several tens of thousands of participants will be required and that children should be included, provided that the candidate vaccine is safe and immunogenic in this group.
KEY MESSAGE
Incidence of Lassa fever is needed to inform vaccine trials. Preliminary results show frequent infections but rare disease, suggesting the need for large vaccine trials.
This abstract is not to be quoted for publication.