Journal Article > CommentaryFull Text
Lancet Microbe. 1 August 2024; Volume 5 (Issue 8); 100881.; DOI:10.1016/S2666-5247(24)00104-6
van Hoek AJ, Funk S, Flasche S, Quilty BJ, van Kleef E, et al.
Lancet Microbe. 1 August 2024; Volume 5 (Issue 8); 100881.; DOI:10.1016/S2666-5247(24)00104-6
Conference Material > Slide Presentation
van Zandvoort K, Bobe M, Hassan AM, Ismail M, Saed M, et al.
MSF Scientific Day International 2023. 7 June 2023; DOI:10.57740/t9ve-m563
Conference Material > Abstract
van Zandvoort K, Bobe M, Buqul A, Ismail M, Saed M, et al.
MSF Scientific Day International 2023. 7 June 2023; DOI:10.57740/cxek-yg24
INTRODUCTION
Despite a likely high burden of disease caused by Streptococcus pneumoniae in humanitarian crises, pneumococcal conjugate vaccines (PCV’s) are rarely used in such settings. Routine immunisation is rarely feasible in crises, and there is little evidence on alternative delivery strategies for PCV. We used modelling to evaluate the effects of different vaccination strategies within humanitarian crisis settings, aiming to identify those which could quickly reduce and sustain low transmission of vaccine serotypes.
METHODS
We conducted a nested carriage and contact survey in a camp for internally displaced people (IDP) in Somaliland to parameterise a transmission model and used it to assess the potential impact and optimal age targeting of PCV campaigns. We extrapolated this model to other representative humanitarian crisis settings: an acute-phase IDP camp, a protracted crisis in a rural setting, and an urban setting with mixed IDP and host communities. For each we explored the impact and efficiency of campaigns with different target age groups and dosing strategies.
ETHICS
This study was approved by the Ethics Review Boards of the London School of Hygiene and Tropical Medicine and the Republic of Somaliland Ministry of Health Development.
RESULTS
We found high prevalence of nasopharyngeal carriage of Streptococcus pneumoniae; 37% (95% confidence interval (CI), 32-42) in all ages, and 76% (95% CI, 70-82) in children <5 years in the Somaliland IDP camp. 53% (95% CI, 45-61) of serotypes are included in the PCV13 vaccine. People had, on average, 9 (9-10) contacts per day, with high mixing rates between children and intergenerational contacts in older age groups. Our model projects that, for the Somaliland IDP camp, a single PCV campaign including children <5 years can temporarily establish substantial herd protection, averting 37% (95% credible interval (CrI) 24-48) of invasive pneumococcal disease cases in the 2 years following the campaign. Extending age eligibility to children up to 10 or 15 years old could further increase this impact by 49% (95% CrI, 39-50) and 53% (95% CrI, 40-64) respectively. Increased migration rates and close contact with unvaccinated host populations reduces the impact. These factors might require wider age targeting and more frequent repeat campaigns until routine services could be re-established.
CONCLUSION
We show that PCV campaigns could be an effective option to reduce the burden of pneumococcal disease in humanitarian crises until routine immunisation can be implemented. Our results are based on modelled estimates, intervention studies are needed to evaluate their feasibility and effectiveness in real settings.
CONFLICTS OF INTEREST
None declared
Despite a likely high burden of disease caused by Streptococcus pneumoniae in humanitarian crises, pneumococcal conjugate vaccines (PCV’s) are rarely used in such settings. Routine immunisation is rarely feasible in crises, and there is little evidence on alternative delivery strategies for PCV. We used modelling to evaluate the effects of different vaccination strategies within humanitarian crisis settings, aiming to identify those which could quickly reduce and sustain low transmission of vaccine serotypes.
METHODS
We conducted a nested carriage and contact survey in a camp for internally displaced people (IDP) in Somaliland to parameterise a transmission model and used it to assess the potential impact and optimal age targeting of PCV campaigns. We extrapolated this model to other representative humanitarian crisis settings: an acute-phase IDP camp, a protracted crisis in a rural setting, and an urban setting with mixed IDP and host communities. For each we explored the impact and efficiency of campaigns with different target age groups and dosing strategies.
ETHICS
This study was approved by the Ethics Review Boards of the London School of Hygiene and Tropical Medicine and the Republic of Somaliland Ministry of Health Development.
RESULTS
We found high prevalence of nasopharyngeal carriage of Streptococcus pneumoniae; 37% (95% confidence interval (CI), 32-42) in all ages, and 76% (95% CI, 70-82) in children <5 years in the Somaliland IDP camp. 53% (95% CI, 45-61) of serotypes are included in the PCV13 vaccine. People had, on average, 9 (9-10) contacts per day, with high mixing rates between children and intergenerational contacts in older age groups. Our model projects that, for the Somaliland IDP camp, a single PCV campaign including children <5 years can temporarily establish substantial herd protection, averting 37% (95% credible interval (CrI) 24-48) of invasive pneumococcal disease cases in the 2 years following the campaign. Extending age eligibility to children up to 10 or 15 years old could further increase this impact by 49% (95% CrI, 39-50) and 53% (95% CrI, 40-64) respectively. Increased migration rates and close contact with unvaccinated host populations reduces the impact. These factors might require wider age targeting and more frequent repeat campaigns until routine services could be re-established.
CONCLUSION
We show that PCV campaigns could be an effective option to reduce the burden of pneumococcal disease in humanitarian crises until routine immunisation can be implemented. Our results are based on modelled estimates, intervention studies are needed to evaluate their feasibility and effectiveness in real settings.
CONFLICTS OF INTEREST
None declared
Journal Article > ResearchFull Text
Epidemics. 1 December 2018; Volume 25; 72-79.; DOI:10.1016/j.epidem.2018.05.008
le Polain de Waroux O, Flasche S, Kucharski AJ, Langendorf C, Ndazima D, et al.
Epidemics. 1 December 2018; Volume 25; 72-79.; DOI:10.1016/j.epidem.2018.05.008
Although patterns of social contacts are believed to be an important determinant of infectious disease transmission, it remains unclear how the frequency and nature of human interactions shape an individual's risk of infection. We analysed data on daily social encounters individually matched to data on S. pneumoniae carriage and acute respiratory symptoms (ARS), from 566 individuals who took part in a survey in South-West Uganda. We found that the frequency of physical (i.e. skin-to-skin), long (≥1 h) and household contacts - which capture some measure of close (i.e. relatively intimate) contact - was higher among pneumococcal carriers than non-carriers, and among people with ARS compared to those without, irrespective of their age. With each additional physical encounter the age-adjusted risk of carriage and ARS increased by 6% (95%CI 2-9%) and 7% (2-13%) respectively. In contrast, the number of casual contacts (<5 min long) was not associated with either pneumococcal carriage or ARS. A detailed analysis by age of contacts showed that the number of close contacts with young children (<5 years) was particularly higher among older children and adult carriers than non-carriers, while the higher number of contacts among people suffering from ARS was more homogeneous across contacts of all ages. Our findings provide key evidence that the frequency of close interpersonal contact is important for transmission of respiratory infections, but not that of casual contacts. Those results are essential for both improving disease prevention and control efforts as well as informing research on infectious disease dynamics and transmission models, and more studies should be undertaken to further validate our results.
Journal Article > ResearchFull Text
BMC Infect Dis. 11 April 2018; Volume 18 (Issue 1); 172.; DOI:10.1186/s12879-018-3073-1
le Polain de Waroux O, Cohuet S, Ndazima D, Kucharski AJ, Juan-Giner A, et al.
BMC Infect Dis. 11 April 2018; Volume 18 (Issue 1); 172.; DOI:10.1186/s12879-018-3073-1
BACKGROUND
Quantification of human interactions relevant to infectious disease transmission through social contact is central to predict disease dynamics, yet data from low-resource settings remain scarce.
METHODS
We undertook a social contact survey in rural Uganda, whereby participants were asked to recall details about the frequency, type, and socio-demographic characteristics of any conversational encounter that lasted for ≥5 min (henceforth defined as 'contacts') during the previous day. An estimate of the number of 'casual contacts' (i.e. < 5 min) was also obtained.
RESULTS
In total, 566 individuals were included in the study. On average participants reported having routine contact with 7.2 individuals (range 1-25). Children aged 5-14 years had the highest frequency of contacts and the elderly (≥65 years) the fewest (P < 0.001). A strong age-assortative pattern was seen, particularly outside the household and increasingly so for contacts occurring further away from home. Adults aged 25-64 years tended to travel more often and further than others, and males travelled more frequently than females.
CONCLUSION
Our study provides detailed information on contact patterns and their spatial characteristics in an African setting. It therefore fills an important knowledge gap that will help more accurately predict transmission dynamics and the impact of control strategies in such areas.
Quantification of human interactions relevant to infectious disease transmission through social contact is central to predict disease dynamics, yet data from low-resource settings remain scarce.
METHODS
We undertook a social contact survey in rural Uganda, whereby participants were asked to recall details about the frequency, type, and socio-demographic characteristics of any conversational encounter that lasted for ≥5 min (henceforth defined as 'contacts') during the previous day. An estimate of the number of 'casual contacts' (i.e. < 5 min) was also obtained.
RESULTS
In total, 566 individuals were included in the study. On average participants reported having routine contact with 7.2 individuals (range 1-25). Children aged 5-14 years had the highest frequency of contacts and the elderly (≥65 years) the fewest (P < 0.001). A strong age-assortative pattern was seen, particularly outside the household and increasingly so for contacts occurring further away from home. Adults aged 25-64 years tended to travel more often and further than others, and males travelled more frequently than females.
CONCLUSION
Our study provides detailed information on contact patterns and their spatial characteristics in an African setting. It therefore fills an important knowledge gap that will help more accurately predict transmission dynamics and the impact of control strategies in such areas.
Journal Article > ResearchFull Text
Emerg Infect Dis. 1 March 2015; Volume 21 (Issue 3); 393-399.; DOI:10.3201/eid2103.141892
Kucharski AJ, Camacho A, Checchi F, Waldman RJ, Grais RF, et al.
Emerg Infect Dis. 1 March 2015; Volume 21 (Issue 3); 393-399.; DOI:10.3201/eid2103.141892
In some parts of western Africa, Ebola treatment centers (ETCs) have reached capacity. Unless capacity is rapidly scaled up, the chance to avoid a generalized Ebola epidemic will soon diminish. The World Health Organization and partners are considering additional Ebola patient care options, including community care centers (CCCs), small, lightly staffed units that could be used to isolate patients outside the home and get them into care sooner than otherwise possible. Using a transmission model, we evaluated the benefits and risks of introducing CCCs into Sierra Leone's Western Area, where most ETCs are at capacity. We found that use of CCCs could lead to a decline in cases, even if virus transmission occurs between CCC patients and the community. However, to prevent CCC amplification of the epidemic, the risk of Ebola virus-negative persons being exposed to virus within CCCs would have to be offset by a reduction in community transmission resulting from CCC use.
Journal Article > CommentaryFull Text
Vaccine. 23 October 2019; Volume 37; DOI:10.1016/j.vaccine.2019.09.038
van Zandvoort K, Checchi F, Diggle E, Eggo RM, Gadroen K, et al.
Vaccine. 23 October 2019; Volume 37; DOI:10.1016/j.vaccine.2019.09.038
Streptococcus pneumoniae is a common human commensal that causes a sizeable part of the overall childhood mortality in low income settings. Populations affected by humanitarian crises are at especially high risk, because a multitude of risk factors that are enhanced during crises increase pneumococcal transmission and disease severity. Pneumococcal conjugate vaccines (PCVs) provide effective protection and have been introduced into the majority of routine childhood immunisation programmes globally, though several barriers have hitherto limited their uptake during humanitarian crises. When PCV coverage cannot be sustained during crises or when PCV has not been part of routine programmes, mass vaccination campaigns offer a quick acting and programmatically feasible bridging solution until services can be restored. However, we currently face a paucity of evidence on which to base the structure of such campaigns. We believe that, now that PCV can be procured at a substantially reduced price through the Humanitarian Mechanism, this lack of information is a remaining hurdle to PCV use in humanitarian crises. Considering the difficulties in conducting research in crises, we propose an evidence generation pathway consisting of primary data collection in combination with mathematical modelling followed by quasi-experimental evaluation of a PCV intervention, which can inform on optimal vaccination strategies that consider age targeting, dosing regimens and impact duration.
Journal Article > ResearchFull Text
PLoS Curr. 10 February 2015; DOI:10.1371/currents.outbreaks
Camacho A, Kucharski AJ, Aki-Sawyerr Y, White M, Flasche S, et al.
PLoS Curr. 10 February 2015; DOI:10.1371/currents.outbreaks
Between August and November 2014, the incidence of Ebola virus disease (EVD) rose dramatically in several districts of Sierra Leone. As a result, the number of cases exceeded the capacity of Ebola holding and treatment centres. During December, additional beds were introduced, and incidence declined in many areas. We aimed to measure patterns of transmission in different regions, and evaluate whether bed capacity is now sufficient to meet future demand.