scholarly journals Model-informed COVID-19 vaccine prioritization strategies by age and serostatus

Science ◽  
2021 ◽  
Vol 371 (6532) ◽  
pp. 916-921 ◽  
Author(s):  
Kate M. Bubar ◽  
Kyle Reinholt ◽  
Stephen M. Kissler ◽  
Marc Lipsitch ◽  
Sarah Cobey ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Severe Acute Respiratory Syndrome ◽  
Cumulative Incidence ◽  
Acquired Immunity ◽  
Years Of Life Lost ◽  
Serological Tests ◽  
Individual Level ◽  
Transmission Rates ◽  
Effective Transmission ◽  
Transmission Blocking Vaccine

Limited initial supply of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine raises the question of how to prioritize available doses. We used a mathematical model to compare five age-stratified prioritization strategies. A highly effective transmission-blocking vaccine prioritized to adults ages 20 to 49 years minimized cumulative incidence, but mortality and years of life lost were minimized in most scenarios when the vaccine was prioritized to adults greater than 60 years old. Use of individual-level serological tests to redirect doses to seronegative individuals improved the marginal impact of each dose while potentially reducing existing inequities in COVID-19 impact. Although maximum impact prioritization strategies were broadly consistent across countries, transmission rates, vaccination rollout speeds, and estimates of naturally acquired immunity, this framework can be used to compare impacts of prioritization strategies across contexts.

scholarly journals Model-informed COVID-19 vaccine prioritization strategies by age and serostatus

2020 ◽  
Author(s):  
Kate M Bubar ◽  
Kyle Reinholt ◽  
Stephen M Kissler ◽  
Marc Lipsitch ◽  
Sarah Cobey ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Cumulative Incidence ◽  
Acquired Immunity ◽  
Years Of Life Lost ◽  
Serological Tests ◽  
Transmission Blocking ◽  
Individual Level ◽  
Transmission Rates ◽  
Effective Transmission ◽  
Transmission Blocking Vaccine

Limited initial supply of SARS-CoV-2 vaccine raises the question of how to prioritize available doses. Here, we used a mathematical model to compare five age-stratified prioritization strategies. A highly effective transmission-blocking vaccine prioritized to adults ages 20-49 years minimized cumulative incidence, but mortality and years of life lost were minimized in most scenarios when the vaccine was prioritized to adults over 60 years old. Use of individual-level serological tests to redirect doses to seronegative individuals improved the marginal impact of each dose while partially addressing existing inequities in COVID-19 impact. While maximum impact prioritization strategies were broadly consistent across countries, transmission rates, vaccination rollout speeds, and estimates of naturally acquired immunity, this framework can be used to compare impacts of prioritization strategies across contexts.

Naturally acquired immunity to sexual stageP. falciparumparasites

Parasitology ◽  
2016 ◽  
Vol 143 (2) ◽  
pp. 187-198 ◽  
Author(s):  
WILL J. R. STONE ◽  
KATHLEEN W. DANTZLER ◽  
SANDRA K. NILSSON ◽  
CHRIS J. DRAKELEY ◽  
MATTHIAS MARTI ◽  
...  
Keyword(s):  
Current Knowledge ◽  
Acquired Immunity ◽  
Transmission Blocking ◽  
Erythrocyte Surface ◽  
Antibody Titres ◽  
Specific Proteins ◽  
Specialized Form ◽  
Transmission Stage ◽  
Effective Transmission ◽  
Transmission Blocking Vaccine

SUMMARYGametocytes are the specialized form ofPlasmodiumparasites that are responsible for human-to-mosquito transmission of malaria. Transmission of gametocytes is highly effective, but represents a biomass bottleneck for the parasite that has stimulated interest in strategies targeting the transmission stages separately from those responsible for clinical disease. Studying targets of naturally acquired immunity against transmission-stage parasites may reveal opportunities for novel transmission reducing interventions, particularly the development of a transmission blocking vaccine (TBV). In this review, we summarize the current knowledge on immunity against the transmission stages ofPlasmodium. This includes immune responses against epitopes on the gametocyte-infected erythrocyte surface during gametocyte development, as well as epitopes present upon gametocyte activation in the mosquito midgut. We present an analysis of historical data on transmission reducing immunity (TRI), as analysed in mosquito feeding assays, and its correlation with natural recognition of sexual stage specific proteins Pfs48/45 and Pfs230. Although high antibody titres towards either one of these proteins is associated with TRI, the presence of additional, novel targets is anticipated. In conclusion, the identification of novel gametocyte-specific targets of naturally acquired immunity against different gametocyte stages could aid in the development of potential TBV targets and ultimately an effective transmission blocking approach.

scholarly journals Review of Associations between Built Environment Characteristics and Severe Acute Respiratory Syndrome Coronavirus 2 Infection Risk

2021 ◽  
Vol 18 (14) ◽  
pp. 7561
Author(s):  
Jingjing Wang ◽  
Xueying Wu ◽  
Ruoyu Wang ◽  
Dongsheng He ◽  
Dongying Li ◽  
...  
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Built Environment ◽  
Longitudinal Research ◽  
Empirical Studies ◽  
Infection Risk ◽  
Design Guidelines ◽  
Individual Level ◽  
Transit Accessibility ◽  
Level Data ◽  
Transmission Pathways

The coronavirus disease 2019 pandemic has stimulated intensive research interest in its transmission pathways and infection factors, e.g., socioeconomic and demographic characteristics, climatology, baseline health conditions or pre-existing diseases, and government policies. Meanwhile, some empirical studies suggested that built environment attributes may be associated with the transmission mechanism and infection risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, no review has been conducted to explore the effect of built environment characteristics on the infection risk. This research gap prevents government officials and urban planners from creating effective urban design guidelines to contain SARS-CoV-2 infections and face future pandemic challenges. This review summarizes evidence from 25 empirical studies and provides an overview of the effect of built environment on SARS-CoV-2 infection risk. Virus infection risk was positively associated with the density of commercial facilities, roads, and schools and with public transit accessibility, whereas it was negatively associated with the availability of green spaces. This review recommends several directions for future studies, namely using longitudinal research design and individual-level data, considering multilevel factors and extending to diversified geographic areas.

scholarly journals Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Setting-specific Transmission Rates: A Systematic Review and Meta-analysis

2021 ◽  
Author(s):  
Hayley A Thompson ◽  
Andria Mousa ◽  
Amy Dighe ◽  
Han Fu ◽  
Alberto Arnedo-Pena ◽  
...  
Keyword(s):  
Systematic Review ◽  
Severe Acute Respiratory Syndrome ◽  
Negative Binomial ◽  
Meta Analysis ◽  
Contact Tracing ◽  
Binomial Model ◽  
Transmission Potential ◽  
Transmission Rates ◽  
Symptom Status ◽  
Index Cases

Abstract Background Understanding the drivers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission is crucial for control policies, but evidence of transmission rates in different settings remains limited. Methods We conducted a systematic review to estimate secondary attack rates (SARs) and observed reproduction numbers (Robs) in different settings exploring differences by age, symptom status, and duration of exposure. To account for additional study heterogeneity, we employed a beta-binomial model to pool SARs across studies and a negative-binomial model to estimate Robs. Results Households showed the highest transmission rates, with a pooled SAR of 21.1% (95% confidence interval [CI]:17.4–24.8). SARs were significantly higher where the duration of household exposure exceeded 5 days compared with exposure of ≤5 days. SARs related to contacts at social events with family and friends were higher than those for low-risk casual contacts (5.9% vs 1.2%). Estimates of SARs and Robs for asymptomatic index cases were approximately one-seventh, and for presymptomatic two-thirds of those for symptomatic index cases. We found some evidence for reduced transmission potential both from and to individuals younger than 20 years of age in the household context, which is more limited when examining all settings. Conclusions Our results suggest that exposure in settings with familiar contacts increases SARS-CoV-2 transmission potential. Additionally, the differences observed in transmissibility by index case symptom status and duration of exposure have important implications for control strategies, such as contact tracing, testing, and rapid isolation of cases. There were limited data to explore transmission patterns in workplaces, schools, and care homes, highlighting the need for further research in such settings.

scholarly journals Modelling the population-level protection conferred by COVID-19 vaccination

2021 ◽  
Author(s):  
Pranesh Padmanabhan ◽  
Rajat Desikan ◽  
Narendra M Dixit
Keyword(s):  
Mathematical Model ◽  
Severe Acute Respiratory Syndrome ◽  
Dose Response ◽  
Neutralizing Antibodies ◽  
Population Level ◽  
Response Curves ◽  
Post Vaccination ◽  
Dose Response Curves ◽  
Vaccine Availability

Although severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines work predominantly by eliciting neutralizing antibodies (NAbs), how the protection they confer depends on the NAb response to vaccination is unclear. Here, we collated and analysed in vitro dose-response curves of >70 NAbs and constructed a landscape defining the spectrum of neutralization efficiencies of NAbs elicited. We mimicked responses of individuals by sampling NAb subsets of known sizes from the landscape and found that they recapitulated responses of convalescent patients. Combining individual responses with a mathematical model of within-host SARS-CoV-2 infection post-vaccination, we predicted how the population-level protection conferred would increase with the NAb response to vaccination. Our predictions captured the outcomes of vaccination trials. Our formalism may help optimize vaccination protocols, given limited vaccine availability.

scholarly journals How effective was Newfoundland & Labrador’s travel ban to prevent the spread of COVID-19? An agent-based analysis

2021 ◽  
Author(s):  
Dionne M. Aleman ◽  
Benjamin Z. Tham ◽  
Sean J. Wagner ◽  
Justin Semelhago ◽  
Asghar Mohammadi ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Spatial Location ◽  
Contact Tracing ◽  
Infection Rates ◽  
Case Scenario ◽  
Agent Based ◽  
Individual Level ◽  
Transmission Rates ◽  
Imported Cases ◽  
The Uk

AbstractBackgroundTo prevent the spread of COVID-19 in Newfoundland & Labrador (NL), NL implemented a wide travel ban in May 2020. We estimate the effectiveness of this travel ban using a customized agent-based simulation (ABS).MethodsWe built an individual-level ABS to simulate the movements and behaviors of every member of the NL population, including arriving and departing travellers. The model considers individual properties (spatial location, age, comorbidities) and movements between environments, as well as age-based disease transmission with pre-symptomatic, symptomatic, and asymptomatic transmission rates. We examine low, medium, and high travel volume, traveller infection rates, and traveller quarantine compliance rates to determine the effect of travellers on COVID spread, and the ability of contact tracing to contain outbreaks.ResultsInfected travellers increased COVID cases by 2-52x (8-96x) times and peak hospitalizations by 2-49x (8-94x), with (without) contact tracing. Although contact tracing was highly effective at reducing spread, it was insufficient to stop outbreaks caused by travellers in even the best-case scenario, and the likelihood of exceeding contact tracing capacity was a concern in most scenarios. Quarantine compliance had only a small impact on COVID spread; travel volume and infection rate drove spread.InterpretationNL’s travel ban was likely a critically important intervention to prevent COVID spread. Even a small number of infected travellers can play a significant role in introducing new chains of transmission, resulting in exponential community spread and significant increases in hospitalizations, while outpacing contact tracing capabilities. With the presence of more transmissible variants, e.g., the UK variant, prevention of imported cases is even more critical.

scholarly journals Community Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 Disproportionately Affects the Latinx Population During Shelter-in-Place in San Francisco

2020 ◽  
Author(s):  
Gabriel Chamie ◽  
Carina Marquez ◽  
Emily Crawford ◽  
James Peng ◽  
Maya Petersen ◽  
...  
Keyword(s):  
Risk Factors ◽  
Severe Acute Respiratory Syndrome ◽  
San Francisco ◽  
Low Income ◽  
Census Tract ◽  
Cumulative Incidence ◽  
Point Prevalence ◽  
Recent Infection ◽  
Work From Home ◽  
Phylogenetic Lineages

Abstract Background There is an urgent need to understand the dynamics and risk factors driving ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission during shelter-in-place mandates. Methods We offered SARS-CoV-2 reverse-transcription polymerase chain reaction (PCR) and antibody (Abbott ARCHITECT IgG) testing, regardless of symptoms, to all residents (aged ≥4 years) and workers in a San Francisco census tract (population: 5174) at outdoor, community-mobilized events over 4 days. We estimated SARS-CoV-2 point prevalence (PCR positive) and cumulative incidence (antibody or PCR positive) in the census tract and evaluated risk factors for recent (PCR positive/antibody negative) vs prior infection (antibody positive/PCR negative). SARS-CoV-2 genome recovery and phylogenetics were used to measure viral strain diversity, establish viral lineages present, and estimate number of introductions. Results We tested 3953 persons (40% Latinx; 41% White; 9% Asian/Pacific Islander; and 2% Black). Overall, 2.1% (83/3871) tested PCR positive: 95% were Latinx and 52% were asymptomatic when tested; 1.7% of census tract residents and 6.0% of workers (non–census tract residents) were PCR positive. Among 2598 tract residents, estimated point prevalence of PCR positives was 2.3% (95% confidence interval [CI], 1.2%–3.8%): 3.9% (95% CI, 2.0%–6.4%) among Latinx persons vs 0.2% (95% CI, .0–.4%) among non-Latinx persons. Estimated cumulative incidence among residents was 6.1% (95% CI, 4.0%–8.6%). Prior infections were 67% Latinx, 16% White, and 17% other ethnicities. Among recent infections, 96% were Latinx. Risk factors for recent infection were Latinx ethnicity, inability to shelter in place and maintain income, frontline service work, unemployment, and household income <$50 000/year. Five SARS-CoV-2 phylogenetic lineages were detected. Conclusions SARS-CoV-2 infections from diverse lineages continued circulating among low-income, Latinx persons unable to work from home and maintain income during San Francisco’s shelter-in-place ordinance.

scholarly journals Malaria transmission rates estimated from serological data

1993 ◽  
Vol 111 (3) ◽  
pp. 503-524 ◽  
Author(s):  
M. N. Burattini ◽  
E. Massad ◽  
F. A. B. Coutinho
Keyword(s):  
Mathematical Model ◽  
Malaria Transmission ◽  
Compartmental Model ◽  
Parasite Prevalence ◽  
Prevalence Data ◽  
Transmission Rates ◽  
Force Of Infection ◽  
Age Dependent ◽  
Serological Data

SummaryA mathematical model was used to estimate malaria transmission rates based on serological data. The model is minimally stochastic and assumes an age-dependent force of infection for malaria. The transmission rates estimated were applied to a simple compartmental model in order to mimic the malaria transmission.The model has shown a good retrieving capacity for serological and parasite prevalence data.

scholarly journals Low Seroprevalence of SARS-CoV-2 in Rhode Island Blood Donors Determined using Multiple Serological Assay Formats

2020 ◽  
Author(s):  
Daniel J Nesbitt ◽  
Daniel Jin ◽  
Joseph W Hogan ◽  
Philip A Chan ◽  
Melissa J Simon ◽  
...  
Keyword(s):  
Public Health ◽  
Severe Acute Respiratory Syndrome ◽  
Rhode Island ◽  
High Throughput ◽  
Blood Donors ◽  
Health Policies ◽  
Antibody Testing ◽  
Serological Tests ◽  
Public Health Policies ◽  
Seropositive Rate

Epidemic projections and public health policies addressing Coronavirus disease (COVID)-19 have been implemented without data reporting on the seroconversion of the population since scalable antibody testing has only recently become available. We measured the percentage of severe acute respiratory syndrome- Coronavirus-2 (SARS-CoV-2) seropositive individuals from 2,008 blood donors drawn in the state of Rhode Island (RI). We utilized multiple antibody testing platforms, including lateral flow immunoassays (LFAs), enzyme-linked immunosorbent assays (ELISAs) and high throughput serological assays (HTSAs). We report than an estimated seropositive rate of RI blood donors of approximately 0.6% existed in April-May of 2020. These data imply that seroconversion, and thus infection, is likely not widespread within this population. Daily new case rates peaked in RI in late April 2020. We conclude that IgG LFAs and HTSAs are suitable to conduct seroprevalence assays in random populations. More studies will be needed using validated serological tests to improve the precision and report the kinetic progression of seroprevalence estimates.

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