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  1. Article ; Online: A flexible age-dependent, spatially-stratified predictive model for the spread of COVID-19, accounting for multiple viral variants and vaccines.

    Schneider, Kristan Alexander / Tsoungui Obama, Henri Christian Junior / Adil Mahmoud Yousif, Nessma

    PloS one

    2023  Volume 18, Issue 1, Page(s) e0277505

    Abstract: Background: After COVID-19 vaccines received approval, vaccination campaigns were launched worldwide. Initially, these were characterized by a shortage of vaccine supply, and specific risk groups were prioritized. Once supply was guaranteed and ... ...

    Abstract Background: After COVID-19 vaccines received approval, vaccination campaigns were launched worldwide. Initially, these were characterized by a shortage of vaccine supply, and specific risk groups were prioritized. Once supply was guaranteed and vaccination coverage saturated, the focus shifted from risk groups to anti-vaxxers, the under-aged population, and regions of low coverage. At the same time, hopes to reach herd immunity by vaccination campaigns were put into perspective by the emergence and spread of more contagious and aggressive viral variants. Particularly, concerns were raised that not all vaccines protect against the new-emerging variants. The objective of this study is to introduce a predictive model to quantify the effect of vaccination campaigns on the spread of SARS-CoV-2 viral variants.
    Methods and findings: The predictive model introduced here is a comprehensive extension of the one underlying the pandemic preparedness tool CovidSim 2.0 (http://covidsim.eu/). The model is age and spatially stratified, incorporates a finite (but arbitrary) number of different viral variants, and incorporates different vaccine products. The vaccines are allowed to differ in their vaccination schedule, vaccination rates, the onset of vaccination campaigns, and their effectiveness. These factors are also age and/or location dependent. Moreover, the effectiveness and the immunizing effect of vaccines are assumed to depend on the interaction of a given vaccine and viral variant. Importantly, vaccines are not assumed to immunize perfectly. Individuals can be immunized completely, only partially, or fail to be immunized against one or many viral variants. Not all individuals in the population are vaccinable. The model is formulated as a high-dimensional system of differential equations, which is implemented efficiently in the programming language Julia. As an example, the model was parameterized to reflect the epidemic situation in Germany until November 2021 and future dynamics of the epidemic under different interventions were predicted. In particular, without tightening contact reductions, a strong epidemic wave is predicted during December 2021 and January 2022. Provided the dynamics of the epidemic in Germany, in late 2021 administration of full-dose vaccination to all eligible individuals (e.g. by mandatory vaccination) would be too late to have a strong effect on reducing the number of infections in the fourth wave in Germany. However, it would reduce mortality. An emergency brake, i.e., an incidence-based stepwise lockdown, would be efficient to reduce the number of infections and mortality. Furthermore, to specifically account for mobility between regions, the model was applied to two German provinces of particular interest: Saxony, which currently has the lowest vaccine rollout in Germany and high incidence, and Schleswig-Holstein, which has high vaccine rollout and low incidence.
    Conclusions: A highly sophisticated and flexible but easy-to-parameterize model for the ongoing COVID-19 pandemic is introduced. The model is capable of providing useful predictions for the COVID-19 pandemic, and hence provides a relevant tool for epidemic decision-making. The model can be adjusted to any country, and the predictions can be used to derive the demand for hospital or ICU capacities.
    MeSH term(s) Humans ; Aged ; COVID-19/epidemiology ; COVID-19/prevention & control ; COVID-19 Vaccines ; Pandemics ; SARS-CoV-2 ; Communicable Disease Control ; Vaccines ; Vaccination
    Chemical Substances COVID-19 Vaccines ; Vaccines
    Language English
    Publishing date 2023-01-20
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2267670-3
    ISSN 1932-6203 ; 1932-6203
    ISSN (online) 1932-6203
    ISSN 1932-6203
    DOI 10.1371/journal.pone.0277505
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: The many definitions of multiplicity of infection.

    Schneider, Kristan Alexander / Tsoungui Obama, Henri Christian Junior / Kamanga, George / Kayanula, Loyce / Adil Mahmoud Yousif, Nessma

    Frontiers in epidemiology

    2022  Volume 2, Page(s) 961593

    Abstract: The presence of multiple genetically different pathogenic variants within the same individual host is common in infectious diseases. Although this is neglected in some diseases, it is well recognized in others like malaria, where it is typically referred ...

    Abstract The presence of multiple genetically different pathogenic variants within the same individual host is common in infectious diseases. Although this is neglected in some diseases, it is well recognized in others like malaria, where it is typically referred to as multiplicity of infection (MOI) or complexity of infection (COI). In malaria, with the advent of molecular surveillance, data is increasingly being available with enough resolution to capture MOI and integrate it into molecular surveillance strategies. The distribution of MOI on the population level scales with transmission intensities, while MOI on the individual level is a confounding factor when monitoring haplotypes of particular interests, e.g., those associated with drug-resistance. Particularly, in high-transmission areas, MOI leads to a discrepancy between the likelihood of a haplotype being observed in an infection (prevalence) and its abundance in the pathogen population (frequency). Despite its importance, MOI is not universally defined. Competing definitions vary from verbal ones to those based on concise statistical frameworks. Heuristic approaches to MOI are popular, although they do not mine the full potential of available data and are typically biased, potentially leading to misinferences. We introduce a formal statistical framework and suggest a concise definition of MOI and its distribution on the host-population level. We show how it relates to alternative definitions such as the number of distinct haplotypes within an infection or the maximum number of alleles detectable across a set of genetic markers. It is shown how alternatives can be derived from the general framework. Different statistical methods to estimate the distribution of MOI and pathogenic variants at the population level are discussed. The estimates can be used as plug-ins to reconstruct the most probable MOI of an infection and set of infecting haplotypes in individual infections. Furthermore, the relation between prevalence of pathogenic variants and their frequency (relative abundance) in the pathogen population in the context of MOI is clarified, with particular regard to seasonality in transmission intensities. The framework introduced here helps to guide the correct interpretation of results emerging from different definitions of MOI. Especially, it excels comparisons between studies based on different analytical methods.
    Language English
    Publishing date 2022-10-05
    Publishing country Switzerland
    Document type Journal Article
    ISSN 2674-1199
    ISSN (online) 2674-1199
    DOI 10.3389/fepid.2022.961593
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Predicting the impact of COVID-19 vaccination campaigns - a flexible age-dependent, spatially-stratified predictive model, accounting for multiple viral variants and vaccines

    Schneider, Kristan Alexander / Tsoungui Obama, Henri Christian Junior / Adil Mahmoud Yousif, Nessma / Ngougoue Ngougoue, Pierre Marie

    medRxiv

    Abstract: Background: After COVID-19 vaccines received approval, vaccination campaigns were launched worldwide. Initially, these were characterized by a shortage of vaccine supply, and specific risk groups were prioritized. Once supply was guaranteed and ... ...

    Abstract Background: After COVID-19 vaccines received approval, vaccination campaigns were launched worldwide. Initially, these were characterized by a shortage of vaccine supply, and specific risk groups were prioritized. Once supply was guaranteed and vaccination coverage saturated, the focus shifted from risk groups to anti-vaxxers, the underaged population, and regions of low coverage. At the same time, hopes to reach herd immunity by vaccination campaigns were put into perspective by the emergence and spread of more contagious and aggressive viral variants. Particularly, concerns were raised that not all vaccines protect against the new-emerging variants. Methods and findings: A model designed to predict the effect of vaccination campaigns on the spread of viral variants is introduced. The model is a comprehensive extension of the model underlying the pandemic preparedness tool CovidSim 2.0 (http://covidsim.eu/). The model is age and spatially stratified, incorporates a finite (but arbitrary) number of different viral variants, and incorporates different vaccine products. The vaccines are allowed to differ in their vaccination schedule, vaccination rates, the onset of vaccination campaigns, and their effectiveness. These factors are also age and/or location dependent. Moreover, the effectiveness and the immunizing effect of vaccines are assumed to depend on the interaction of a given vaccine and viral variant. Importantly, vaccines are not assumed to immunize perfectly. Individuals can be immunized completely, only partially, or fail to be immunized against one or many viral variants. Not all individuals in the population are vaccinable. The model is formulated as a high-dimensional system of differential equations, which is implemented efficiently in the programming language Julia. As an example, the model was parameterized to reflect the epidemic situation in Germany until November 2021 and predicted the future dynamics of the epidemic under different interventions. In particular, without tightening contact reductions, a strong epidemic wave is predicted. At the current state, mandatory vaccination would be too late to have a strong effect on reducing the number of infections. However, it would reduce mortality. An emergency brake, i.e., an incidence-based stepwise lockdown would be efficient to reduce the number of infections and mortality. Furthermore, to specifically account for mobility between regions, the model was applied to two German provinces of particular interest: Saxony, which currently has the lowest vaccine rollout in Germany and high incidence, and Schleswig-Holstein, which has high vaccine rollout and low incidence. Conclusions: A highly sophisticated and flexible but easy-to-parameterize model for the ongoing COVID-19 pandemic is introduced. The model is capable of providing useful predictions for the COVID-19 pandemic, and hence provides a relevant tool for epidemic decision-making. The model can be adjusted to any country, to derive the demand for hospital and ICU capacities as well as economic collateral damages.
    Keywords covid19
    Language English
    Publishing date 2022-01-01
    Publisher Cold Spring Harbor Laboratory Press
    Document type Article ; Online
    DOI 10.1101/2021.12.29.21268526
    Database COVID19

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  4. Article ; Online: Preventing COVID-19 spread in closed facilities by regular testing of employees-An efficient intervention in long-term care facilities and prisons?

    Tsoungui Obama, Henri Christian Junior / Adil Mahmoud Yousif, Nessma / Alawam Nemer, Looli / Ngougoue Ngougoue, Pierre Marie / Ngwa, Gideon Akumah / Teboh-Ewungkem, Miranda / Schneider, Kristan Alexander

    PloS one

    2021  Volume 16, Issue 4, Page(s) e0249588

    Abstract: Background: Different levels of control measures were introduced to contain the global COVID-19 pandemic, many of which have been controversial, particularly the comprehensive use of diagnostic tests. Regular testing of high-risk individuals (pre- ... ...

    Abstract Background: Different levels of control measures were introduced to contain the global COVID-19 pandemic, many of which have been controversial, particularly the comprehensive use of diagnostic tests. Regular testing of high-risk individuals (pre-existing conditions, older than 60 years of age) has been suggested by public health authorities. The WHO suggested the use of routine screening of residents, employees, and visitors of long-term care facilities (LTCF) to protect the resident risk group. Similar suggestions have been made by the WHO for other closed facilities including incarceration facilities (e.g., prisons or jails), wherein parts of the U.S., accelerated release of approved inmates is taken as a measure to mitigate COVID-19.
    Methods and findings: Here, the simulation model underlying the pandemic preparedness tool CovidSim 1.1 (http://covidsim.eu/) is extended to investigate the effect of regularly testing of employees to protect immobile resident risk groups in closed facilities. The reduction in the number of infections and deaths within the risk group is investigated. Our simulations are adjusted to reflect the situation of LTCFs in Germany, and incarceration facilities in the U.S. COVID-19 spreads in closed facilities due to contact with infected employees even under strict confinement of visitors in a pandemic scenario without targeted protective measures. Testing is only effective in conjunction with targeted contact reduction between the closed facility and the outside world-and will be most inefficient under strategies aiming for herd immunity. The frequency of testing, the quality of tests, and the waiting time for obtaining test results have noticeable effects. The exact reduction in the number of cases depends on disease prevalence in the population and the levels of contact reductions. Testing every 5 days with a good quality test and a processing time of 24 hours can lead up to a 40% reduction in the number of infections. However, the effects of testing vary substantially among types of closed facilities and can even be counterproductive in U.S. IFs.
    Conclusions: The introduction of COVID-19 in closed facilities is unavoidable without a thorough screening of persons that can introduce the disease into the facility. Regular testing of employees in closed facilities can contribute to reducing the number of infections there, but is only meaningful as an accompanying measure, whose economic benefit needs to be assessed carefully.
    MeSH term(s) COVID-19/diagnosis ; COVID-19/prevention & control ; COVID-19 Testing ; Humans ; Long-Term Care ; Mass Screening ; Nursing Homes ; Prisons ; SARS-CoV-2/isolation & purification
    Language English
    Publishing date 2021-04-22
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2267670-3
    ISSN 1932-6203 ; 1932-6203
    ISSN (online) 1932-6203
    ISSN 1932-6203
    DOI 10.1371/journal.pone.0249588
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: The impact of COVID-19 vaccination campaigns accounting for antibody-dependent enhancement.

    Adil Mahmoud Yousif, Nessma / Tsoungui Obama, Henri Christian Junior / Ngucho Mbeutchou, Yvan Jordan / Kwamou Ngaha, Sandy Frank / Kayanula, Loyce / Kamanga, George / Ibrahim, Toheeb Babatunde / Bwanu Iliya, Patience / Iyanda, Sulyman / Alawam Nemer, Looli / Helle, Kristina Barbara / Teboh-Ewungkem, Miranda Ijang / Schneider, Kristan Alexander

    PloS one

    2021  Volume 16, Issue 4, Page(s) e0245417

    Abstract: Background: COVID-19 vaccines are approved, vaccination campaigns are launched, and worldwide return to normality seems within close reach. Nevertheless, concerns about the safety of COVID-19 vaccines arose, due to their fast emergency approval. In fact, ...

    Abstract Background: COVID-19 vaccines are approved, vaccination campaigns are launched, and worldwide return to normality seems within close reach. Nevertheless, concerns about the safety of COVID-19 vaccines arose, due to their fast emergency approval. In fact, the problem of antibody-dependent enhancement was raised in the context of COVID-19 vaccines.
    Methods and findings: We introduce a complex extension of the model underlying the pandemic preparedness tool CovidSim 1.1 (http://covidsim.eu/) to optimize vaccination strategies with regard to the onset of campaigns, vaccination coverage, vaccination schedules, vaccination rates, and efficiency of vaccines. Vaccines are not assumed to immunize perfectly. Some individuals fail to immunize, some reach only partial immunity, and-importantly-some develop antibody-dependent enhancement, which increases the likelihood of developing symptomatic and severe episodes (associated with higher case fatality) upon infection. Only a fraction of the population will be vaccinated, reflecting vaccination hesitancy or contraindications. The model is intended to facilitate decision making by exploring ranges of parameters rather than to be fitted by empirical data. We parameterized the model to reflect the situation in Germany and predict increasing incidence (and prevalence) in early 2021 followed by a decline by summer. Assuming contact reductions (curfews, social distancing, etc.) to be lifted in summer, disease incidence will peak again. Fast vaccine deployment contributes to reduce disease incidence in the first quarter of 2021, and delay the epidemic outbreak after the summer season. Higher vaccination coverage results in a delayed and reduced epidemic peak. A coverage of 75%-80% is necessary to prevent an epidemic peak without further drastic contact reductions.
    Conclusions: With the vaccine becoming available, compliance with contact reductions is likely to fade. To prevent further economic damage from COVID-19, high levels of immunization need to be reached before next year's flu season, and vaccination strategies and disease management need to be flexibly adjusted. The predictive model can serve as a refined decision support tool for COVID-19 management.
    MeSH term(s) Antibody-Dependent Enhancement ; COVID-19/epidemiology ; COVID-19/prevention & control ; COVID-19 Vaccines/therapeutic use ; Germany/epidemiology ; Humans ; Immunization Programs ; Immunization Schedule ; SARS-CoV-2/physiology ; Software
    Chemical Substances COVID-19 Vaccines
    Language English
    Publishing date 2021-04-22
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2267670-3
    ISSN 1932-6203 ; 1932-6203
    ISSN (online) 1932-6203
    ISSN 1932-6203
    DOI 10.1371/journal.pone.0245417
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Preventing COVID-19 spread in closed facilities by regular testing of employees-An efficient intervention in long-term care facilities and prisons?

    Henri Christian Junior Tsoungui Obama / Nessma Adil Mahmoud Yousif / Looli Alawam Nemer / Pierre Marie Ngougoue Ngougoue / Gideon Akumah Ngwa / Miranda Teboh-Ewungkem / Kristan Alexander Schneider

    PLoS ONE, Vol 16, Iss 4, p e

    2021  Volume 0249588

    Abstract: Background Different levels of control measures were introduced to contain the global COVID-19 pandemic, many of which have been controversial, particularly the comprehensive use of diagnostic tests. Regular testing of high-risk individuals (pre-existing ...

    Abstract Background Different levels of control measures were introduced to contain the global COVID-19 pandemic, many of which have been controversial, particularly the comprehensive use of diagnostic tests. Regular testing of high-risk individuals (pre-existing conditions, older than 60 years of age) has been suggested by public health authorities. The WHO suggested the use of routine screening of residents, employees, and visitors of long-term care facilities (LTCF) to protect the resident risk group. Similar suggestions have been made by the WHO for other closed facilities including incarceration facilities (e.g., prisons or jails), wherein parts of the U.S., accelerated release of approved inmates is taken as a measure to mitigate COVID-19. Methods and findings Here, the simulation model underlying the pandemic preparedness tool CovidSim 1.1 (http://covidsim.eu/) is extended to investigate the effect of regularly testing of employees to protect immobile resident risk groups in closed facilities. The reduction in the number of infections and deaths within the risk group is investigated. Our simulations are adjusted to reflect the situation of LTCFs in Germany, and incarceration facilities in the U.S. COVID-19 spreads in closed facilities due to contact with infected employees even under strict confinement of visitors in a pandemic scenario without targeted protective measures. Testing is only effective in conjunction with targeted contact reduction between the closed facility and the outside world-and will be most inefficient under strategies aiming for herd immunity. The frequency of testing, the quality of tests, and the waiting time for obtaining test results have noticeable effects. The exact reduction in the number of cases depends on disease prevalence in the population and the levels of contact reductions. Testing every 5 days with a good quality test and a processing time of 24 hours can lead up to a 40% reduction in the number of infections. However, the effects of testing vary substantially among types of ...
    Keywords Medicine ; R ; Science ; Q
    Language English
    Publishing date 2021-01-01T00:00:00Z
    Publisher Public Library of Science (PLoS)
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  7. Article ; Online: Preventing COVID-19 spread in closed facilities by regular testing of employees – an efficient intervention in long-term care facilities and prisons

    Tsoungui Obama, Henri Christian Junior / Adil Mahmoud Yousif, Nessma / Hassan Mohamed Alawam Nemer, Looli / Ngougoue Ngougoue, Pierre Marie / Ngwa, Gideon Akumah / Teboh-Ewungkem, Miranda / Schneider, Kristan

    medRxiv

    Abstract: Background: Draconic control measures were introduced to contain the global COVID-19 pandemic, many of which have been controversial, particularly the comprehensive use of diagnostic tests. Regular testing of high-risk individuals (pre-existing ... ...

    Abstract Background: Draconic control measures were introduced to contain the global COVID-19 pandemic, many of which have been controversial, particularly the comprehensive use of diagnostic tests. Regular testing of high-risk individuals (pre-existing conditions, older than 60 years of age) has been suggested by public health authorities. The WHO suggested the use of routine screening of residents, employees, and visitors of long-term care facilities (LTCF) to protect the resident risk group. Similar suggestions have been made by the WHO for other closed facilities including incarceration facilities (e.g., prisons or jails), where in parts of the US, accelerated release of approved inmates is taken as a measure to mitigate COVID-19. Methods and findings: Here, the simulation model underlying the pandemic preparedness tool CovidSim 1.1 (http://covidsim.eu/) is extended to investigate the effect of regularly testing of employees in order to protect immobile resident risk groups in closed facilities. The reduction in the number of infections and deaths within the risk group are investigated as well as the potential economic gain resulting from savings in COVID-19 related treatment costs in comparison to costs resulting from the testing interventions. Our simulations are adjusted to reflect the situation of LTCFs in the Federal Republic of Germany. The probability is nearly one that COVID-19 spreads into closed facilities due to contact with infected employees even under strict confinement of visitors in a pandemic scenario without targeted protective measures. Regular screening of all employees by PCR tests provides a significant reduction of COVID-19 cases and related deaths in LTCFs. While the frequency of testing (testing rate) and the quality of tests have noticeable effects, the waiting time for obtaining test results (ranging from 12 up to 96 hours) hardly impacts the outcome. The results suggest that testing every two weeks with low-quality tests and a processing time of up to 96 hours yields a strong reduction in the number of cases. Rough estimates suggest a significant economic gain. Conclusions: The introduction of COVID-19 in closed facilities is unavoidable without thorough screening of persons that can introduce the disease into the facility. These measures provide an economically meaningful way to protect vulnerable risk groups characterized by an elevated risk of severe infections in closed facilities, in which contact-reducing measures are difficult to implement due to imminent unavoidable close human-to-human contacts.
    Keywords covid19
    Language English
    Publishing date 2020-10-14
    Publisher Cold Spring Harbor Laboratory Press
    Document type Article ; Online
    DOI 10.1101/2020.10.12.20211573
    Database COVID19

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