scholarly journals Combining serological and contact data to derive target immunity levels for achieving and maintaining measles elimination

2017 ◽  
Author(s):  
Sebastian Funk ◽  
Jennifer K. Knapp ◽  
Emmaculate Lebo ◽  
Susan E. Reef ◽  
Alya J. Dabbagh ◽  
...  
Keyword(s):  
Measles Virus ◽  
Herd Immunity ◽  
Age Groups ◽  
Threshold Level ◽  
Specific Immunity ◽  
Measles Elimination ◽  
Contact Patterns ◽  
Wide Range ◽  
Contact Data ◽  
Serological Studies

AbstractBackgroundVaccination has reduced the global incidence of measles to the lowest rates in history. However, local interruption of measles virus transmission requires sustained high levels of population immunity that can be challenging to achieve and maintain. The herd immunity threshold for measles is typically stipulated at 90–95%. This figure does not easily translate into age-specific immunity levels required to interrupt transmission. Previous estimates of such levels were based on speculative contact patterns based on historical data from high-income countries. The aim of this study was to determine age-specific immunity levels that would ensure elimination of measles when taking into account empirically observed contact patterns.MethodsWe combined estimated immunity levels from serological data in 17 countries with studies of age-specific mixing patterns to derive contact-adjusted immunity levels. We then compared these to case data from the 10 years following the seroprevalence studies to establish a contact-adjusted immunity threshold for elimination. We lastly combined a range of hypothetical immunity profiles with contact data from a wide range of socioeconomic and demographic settings to determine whether they would be sufficient for elimination.ResultsWe found that contact-adjusted immunity levels were able to predict whether countries would experience outbreaks in the decade following the serological studies in about 70% of countries. The corresponding threshold level of contact-adjusted immunity was found to be 93%, corresponding to an average basic reproduction number of approximately 14. Testing different scenarios of immunity with this threshold level using contact studies from around the world, we found that 95% immunity would have to be achieved by the age of five and maintained across older age groups to guarantee elimination. This reflects a greater level of immunity required in 5–9 year olds than established previously.ConclusionsThe immunity levels we found necessary for measles elimination are higher than previous guidance. The importance of achieving high immunity levels in 5–9 year olds presents both a challenge and an opportunity. While such high levels can be difficult to achieve, school entry provides an opportunity to ensure sufficient vaccination coverage. Combined with observations of contact patterns, further national and sub-national serological studies could serve to highlight key gaps in immunity that need to be filled in order to achieve national and regional measles elimination.

scholarly journals Combining serological and contact data to derive target immunity levels for achieving and maintaining measles elimination

BMC Medicine ◽  
2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Sebastian Funk ◽  
Jennifer K. Knapp ◽  
Emmaculate Lebo ◽  
Susan E. Reef ◽  
Alya J. Dabbagh ◽  
...  
Keyword(s):  
Measles Virus ◽  
Herd Immunity ◽  
Age Groups ◽  
Threshold Level ◽  
Specific Immunity ◽  
Measles Elimination ◽  
Contact Patterns ◽  
Wide Range ◽  
Contact Data ◽  
Serological Studies

Abstract Background Vaccination has reduced the global incidence of measles to the lowest rates in history. However, local interruption of measles virus transmission requires sustained high levels of population immunity that can be challenging to achieve and maintain. The herd immunity threshold for measles is typically stipulated at 90–95%. This figure does not easily translate into age-specific immunity levels required to interrupt transmission. Previous estimates of such levels were based on speculative contact patterns based on historical data from high-income countries. The aim of this study was to determine age-specific immunity levels that would ensure elimination of measles when taking into account empirically observed contact patterns. Methods We combined estimated immunity levels from serological data in 17 countries with studies of age-specific mixing patterns to derive contact-adjusted immunity levels. We then compared these to case data from the 10 years following the seroprevalence studies to establish a contact-adjusted immunity threshold for elimination. We lastly combined a range of hypothetical immunity profiles with contact data from a wide range of socioeconomic and demographic settings to determine whether they would be sufficient for elimination. Results We found that contact-adjusted immunity levels were able to predict whether countries would experience outbreaks in the decade following the serological studies in about 70% of countries. The corresponding threshold level of contact-adjusted immunity was found to be 93%, corresponding to an average basic reproduction number of approximately 14. Testing different scenarios of immunity with this threshold level using contact studies from around the world, we found that 95% immunity would have to be achieved by the age of five and maintained across older age groups to guarantee elimination. This reflects a greater level of immunity required in 5–9-year-olds than established previously. Conclusions The immunity levels we found necessary for measles elimination are higher than previous guidance. The importance of achieving high immunity levels in 5–9-year-olds presents both a challenge and an opportunity. While such high levels can be difficult to achieve, school entry provides an opportunity to ensure sufficient vaccination coverage. Combined with observations of contact patterns, further national and sub-national serological studies could serve to highlight key gaps in immunity that need to be filled in order to achieve national and regional measles elimination.

scholarly journals A herd immunity to measles and rubella viruses in the population of the Republic of Serbia

2021 ◽  
Vol 11 (1) ◽  
pp. 171-176
Author(s):  
M. A. Bichurina ◽  
S. Filipovic-Vignjevic ◽  
A. Yu. Antipova ◽  
M. Bancevic ◽  
I. N. Lavrentieva
Keyword(s):  
Measles Virus ◽  
Herd Immunity ◽  
Age Groups ◽  
Age Group ◽  
Igg Antibodies ◽  
Mmr Vaccine ◽  
Igg Antibody ◽  
Group I ◽  
Study Results ◽  
The Republic

According to the WHO Strategic Plan, measles should be eradicated in 2020 in the five WHO Regions including European Region. However, large measles outbreaks are being periodically registered in diverse European countries. In the Republic of Serbia (SRB), 5,076 measles cases were detected in 2018, among which 15 cases were fatal.Aim of the study was to examine herd immunity to measles and rubella viruses in the population of the Republic of Serbia.Materials and methods. Blood serum samples obtained in 2018 and 2019 from conditionally healthy residents of the Republic of Serbia were tested for the presence of IgG antibodies to measles and rubella viruses in five age groups: I — children from 2 to 6 years old, II — children from 8 to 14 years old, III — 15 to 24 years old, IV — 25 to 49 years old and V — over 50 years old. A total of 1000 samples were obtained, 200 sera in each group. Enzygnost® Anti-Measles virus/IgG and Enzygnost® Anti-Rubella virus/IgG ELISA test systems (Siemens Healthcare Diagnostics Products GmbH, Germany) were used according to the manufacturer's instructions.Results. Overall, around 23.0% and 33.7% of the surveyed persons had no or low level of anti-measles IgG antibody (≥ 275.0 — ≤ 1000.0 IU/1). In age group I, 60% children contained no or “low” anti-measles antibodies titer (29.5% and 30.5%, respectively). In addition, low antibody titer level was mainly detected in individuals from age group II and III (p < 0.05). A third of children under 8—14 contained high IgG-antibodies titer against measles (> 3000.0 IU/l) that might serve as an evidence that such subjects recently recovered after measles. Similar results were obtained for IgG antibodies to rubella in the same age groups.Discussion. The study results evidence about altered routine immunization against measles and rubella in children aged 12—15 months (first vaccination) and those at age of 6—7 years (revaccination) with MMR vaccine. The data obtained correlate with official data on coverage with measles and rubella vaccines in the Republic of Serbia.

scholarly journals A survey of examining herd measles immunity in adults over 35 years old

2020 ◽  
Vol 10 (2) ◽  
pp. 381-386 ◽  
Author(s):  
L. V. Rubis
Keyword(s):  
Measles Virus ◽  
High Titer ◽  
Herd Immunity ◽  
Age Groups ◽  
High Risk Group ◽  
Protective Level ◽  
Protective Antibody ◽  
The Republic ◽  
High Level ◽  
Post Infectious

A high measles incidence rate has been registered in Russia in recent years, with adults being actively involved in the epidemic process (about 40% of patients), thereby underlying relevance of assessing herd immunity in different  age groups to measure its risk. The data on examining serum antibodies to measles virus in 402 residents of Petrozavodsk are shown: 164 and 238 subjects were born in 1948–1968 (51–71 years) and 1970–1983 (36–50 years), respectively. It was found that the second group had significantly higher percentage not only of seropositive persons (94.1±1.5 vs. 77.4±3.3%, respectively), but also frequency of detected high IgG level (5 and more IU/l) reaching 39.7±3.5 vs. 15.4±5.8%, respectively. Analysis of vaccination history showed that of 351 people with protective antibody levels, 20.9% were vaccinated once or twice, 14 of them in childhood and 63 within the 15 years prior to the study. Of the 51 people with no measles antibodies or below protective level, 13.7% were vaccinated: five in childhood, and two within the last 15 years. Among those who was born in 1948–1968, 87.1±2.2% provided no information about previous vaccinations and probably were not vaccinated. In this group, percentage of those examined with a protective antibody level was significantly higher than in the 36–50 years group — 87.1±2.2 and 62.2±4.3%, respectively. In addition, 23 subjects confirmed that they recovered after measles in childhood. Of these, antibodies were detected in 21 subjects, including 9 having serum titer at level of 5 or more IU/ml. Until 1969, the Republic of Karelia registered a high level of measles morbidity (477–2176,0 per 100 thousand). The predominance in the group born before 1969, individuals seropositive to measles mainly at high titer, indicates that intense post-infectious immunity was preserved. The lack of protective level of antibodies to measles virus in 22.6% of persons aged 36–50 years (1969–1983 year of birth), due to the low level of post-infectious and insufficient durability of post-vaccination immunity allowing to definer them as a high risk group for measles infection.

scholarly journals Influence of heterogeneous age-group contact patterns on critical vaccination rates for herd immunity to SARS-CoV-2

2021 ◽  
Author(s):  
Joan Saldana ◽  
Caterina M Scoglio
Keyword(s):  
Vaccination Coverage ◽  
Herd Immunity ◽  
Age Groups ◽  
Social Contact ◽  
Vaccination Strategy ◽  
Primary Concern ◽  
Vaccination Rates ◽  
Contact Patterns ◽  
Group Contact ◽  
Age Structured

Currently, several western countries have more than half of their population fully vaccinated against COVID-19. At the same time, some of them are experiencing a fourth or even a fifth wave of cases, most of them concentrated in sectors of the populations whose vaccination coverage is lower than the average. So, the initial scenario of vaccine prioritization has given way to a new one where achieving herd immunity is the primary concern. Using an age-structured vaccination model with waning immunity, we show that, under a limited supply of vaccines, a vaccination strategy based on minimizing the basic reproduction number allows for the deployment of a number of vaccine doses lower than the one required for maximizing the vaccination coverage. Such minimization is achieved by giving greater protection to those age groups that, for a given social contact pattern, have smaller fractions of susceptible individuals at the endemic equilibrium without vaccination, that is, to those groups that are more vulnerable to infection.

scholarly journals Herd immunity to SARS-CoV-2 among the population of the Republic of Belarus amid the COVID-19 pandemic

2021 ◽  
Vol 11 (5) ◽  
pp. 887-904
Author(s):  
A. Yu. Popova ◽  
A. A. Tarasenko ◽  
V. Yu. Smolensky ◽  
S. A. Egorova ◽  
V. S. Smirnov ◽  
...  
Keyword(s):  
Herd Immunity ◽  
Age Groups ◽  
Statistical Processing ◽  
Threshold Level ◽  
Test System ◽  
Elisa Test ◽  
Surface Glycoprotein ◽  
Pasteur Institute ◽  
The Republic ◽  
Questionnaire Method

Objective was to investigate the SARS-CoV-2 collective immunity status of the population of Belarus within the context of the COVID-19 pandemic. Materials and methods. The work was carried out according to the methodology for assessing SARS-CoV-2 population immunity, developed by Rospotrebnadzor Russia and the Ministry of Health of Belarus with the participation of the St. Petersburg Pasteur Institute, taking into account WHO recommendations. The Bioethics Committee of Belarus and the local ethics committee of the St. Petersburg Pasteur Institute approved the study. Selection of participants was carried out using a questionnaire method and online technology (internet, cloud server). Volunteers were randomized into seven age groups (years of age): 1–17; 18–29; 30–39; 40–49; 50–59; 60–69; and 70+. Regional randomization ensured proportional representation of volunteers from each region, and no more than 30 people were included from one enterprise. In accordance with manufacturer instructions, blood plasma samples were analyzed for: IgG antibodies (Abs) to the SARS-CoV-2 nucleocapsid (Nc) using a quantitative ELISA test system; and IgG Abs to the receptor binding domain (RBD) of the SARS-CoV-2 S (spike) surface glycoprotein using a qualitative ELISA test system. Statistical processing was carried out using Excel 2010 and other software. Statistical differences were designated as significant when p < 0.05, unless otherwise indicated. Results. The level of seroprevalence, in terms of Abs to Nc among the Belarusian population, was 38.4% (95% CI 37.6–45.4). The highest Ab levels were found among individuals in older age groups (50-70+ years old). The lowest were found in children 1–17 years old and in young people 18–39 years old The distribution of seroprevalence across Belarusian regions was relatively homogeneous, with the exception of the Minsk Region, where a statistically significant decrease in the indicator was noted. In terms of profession, the largest share of seropositive individuals was found among transportation workers; the smallest was found in business. The moderate COVID-19 incidence has not led to a dramatic increase in the number of contacts. The base reproduction number (R0) was 1.3. In the Republic of Belarus, there was a moderate level of asymptomatic COVID-19 among seropositive individuals (45.3% [95% CI 44.0–46.7]). This form of infection was observed most often among children aged 1–17 years old (65.0% [95% CI 61.3–68.6]). In parallel with seroprevalence assessment, SARS-CoV-2 vaccination was carried out. We used two vaccines: Gam-COVID-Vac (also known as Sputnik V, developed by Gamaleya National Center for Epidemiology and Microbiology, Russia); and BBIBP-CorV (Sinopharm, PRC). Vaccination against SARS-CoV-2 was accompanied by an increase in the level of anti-RBD Abs (95% [95% CI 94.7–96.7]). Taking into account the vaccination of a subset of the population with BBIBP-CorV, the overall herd immunity, inferred from the analyzed indicators (presence of anti-Nc or anti-RBD Abs), was 47.1% (95% CI 46.3–48.0). Conclusion. COVID-19 in Belarus was characterized by a moderately pronounced course of the epidemic process. The threshold level of herd immunity to SARS-CoV-2 has not yet been reached, as a result of which the conditions for progression of the epidemic remain.

scholarly journals Measles Cases by Age Group during the Elimination of Infection

2017 ◽  
Vol 16 (3) ◽  
pp. 18-25 ◽  
Author(s):  
O. V. Tsvirkun ◽  
A. G. Gerasimova ◽  
N. T. Tikhonova ◽  
E. B. Ezhlova ◽  
A. A. Melnikova ◽  
...  
Keyword(s):  
Measles Virus ◽  
Adult Population ◽  
Age Groups ◽  
First Year ◽  
Age Group ◽  
Epidemic Process ◽  
Leading Role ◽  
Measles Elimination ◽  
Children First ◽  
First Year Of Life

Objective. With the increase in vaccination coverage of the child population began the process of ousting children determining the incidence of measles in the country and by 2004, the children ceased to play a leading role in maintaining the epidemic process of measles. The definition of significance in the epidemic process of measles individuals of different age, including children in the first year of life, was the purpose of the work. Material and methods. Measles cases in different age groups were analyzed for the period 2003 - 2015 in the Russian Federation. 1799 cases of measles in children under 1 year were investigated. The ELISA method were examined the sera of children up to 1 year in 2002 - 22 sampls, 2016 - 31 sampls. Results. Analysis of the incidence of measles in different age groups conducted since the beginning of the program of measles elimination in Russia to date (2003 - 2015), showed that with the increase in the level of the immune stratum, the incidence of measles inculcated among the population declined markedly and even in the boom years (2012 - 2014) intensive morbidity rates of children aged 3 - 6 years, adolescents and adults averages ranged from 3.0 to 4.0 per 100 thousand of the appropriate age. The exception was children first year of life and children aged 1 - 2 years, of intense the incidence of which was several times higher (in average, respectively, was 22.0 and 19.0). If the vast majority of affected children aged 1 - 2 years had been vaccinated against measles, for various reasons, the children of the first year of life, according to the immunization calendar, the vaccination could not be. Conclusion. Detailed analysis showed that the incidence of measles in the country determined by the adult population. Comparison of incidence and state of specific immunity to measles virus in children the first year of life suggests that their involvement in the epidemic process of measles is not determinative. Changing the proportion of affected children of this age are directly linked with fluctuations in the long-term dynamics of the overall incidence of measles in the country, and high, compared with other age groups, the intensive indicator of disease is not due to a large numerical composition of this age group.

scholarly journals COVID-19 Pandemic and Vaccines Update on Challenges and Resolutions

2021 ◽  
Vol 11 ◽  
Author(s):  
Wajihul Hasan Khan ◽  
Zohra Hashmi ◽  
Aditya Goel ◽  
Razi Ahmad ◽  
Kanisha Gupta ◽  
...  
Keyword(s):  
Neutralizing Antibodies ◽  
Viral Vectors ◽  
Rna Virus ◽  
Herd Immunity ◽  
Age Groups ◽  
Host Cells ◽  
Phase Iii ◽  
Vaccine Hesitancy ◽  
Live Attenuated Vaccine ◽  
Wide Range

The coronavirus disease (COVID-19) is caused by a positive-stranded RNA virus called severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), belonging to the Coronaviridae family. This virus originated in Wuhan City, China, and became the cause of a multiwave pandemic that has killed 3.46 million people worldwide as of May 22, 2021. The havoc intensified with the emergence of SARS-CoV-2 variants (B.1.1.7; Alpha, B.1.351; Beta, P.1; Gamma, B.1.617; Delta, B.1.617.2; Delta-plus, B.1.525; Eta, and B.1.429; Epsilon etc.) due to mutations generated during replication. More variants may emerge to cause additional pandemic waves. The most promising approach for combating viruses and their emerging variants lies in prophylactic vaccines. Several vaccine candidates are being developed using various platforms, including nucleic acids, live attenuated virus, inactivated virus, viral vectors, and protein-based subunit vaccines. In this unprecedented time, 12 vaccines against SARS-CoV-2 have been phased in following WHO approval, 184 are in the preclinical stage, and 100 are in the clinical development process. Many of them are directed to elicit neutralizing antibodies against the viral spike protein (S) to inhibit viral entry through the ACE-2 receptor of host cells. Inactivated vaccines, to the contrary, provide a wide range of viral antigens for immune activation. Being an intracellular pathogen, the cytotoxic CD8+ T Cell (CTL) response remains crucial for all viruses, including SARS-CoV-2, and needs to be explored in detail. In this review, we try to describe and compare approved vaccines against SARS-CoV-2 that are currently being distributed either after phase III clinical trials or for emergency use. We discuss immune responses induced by various candidate vaccine formulations; their benefits, potential limitations, and effectiveness against variants; future challenges, such as antibody-dependent enhancement (ADE); and vaccine safety issues and their possible resolutions. Most of the current vaccines developed against SARS-CoV-2 are showing either promising or compromised efficacy against new variants. Multiple antigen-based vaccines (multivariant vaccines) should be developed on different platforms to tackle future variants. Alternatively, recombinant BCG, containing SARS-CoV-2 multiple antigens, as a live attenuated vaccine should be explored for long-term protection. Irrespective of their efficacy, all vaccines are efficient in providing protection from disease severity. We must insist on vaccine compliance for all age groups and work on vaccine hesitancy globally to achieve herd immunity and, eventually, to curb this pandemic.

A Cross Sectional Survey of Chicken Astroviruses Antibody in Broiler and Sonali (Cross-Bred) Chickens in Selected Areas in Bangladesh

2020 ◽  
Vol 43 (1) ◽  
pp. 75-80
Author(s):  
Md Zulfekar Ali ◽  
Mohammad Moktader Moula ◽  
Zafar Ahmed Bhuiyan ◽  
Muhammad Tariq Javed
Keyword(s):  
Age Groups ◽  
Winter Season ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Blood Samples ◽  
Elisa Kit ◽  
Published Report ◽  
Poultry Birds ◽  
Wide Range ◽  
Group B

AbstractChicken astroviruses (CAstV) are enteric viruses of poultry causing gastroenteritis, malabsorption, gout and white chick disease commonly known as runting-stunting syndrome (RSS). It can affect the wide range of poultry birds, especially chicken, turkey and duck worldwide. To our best knowledge there is no published report on presence of antibodies against CAstV in Bangladesh. Therefore, the study aimed to detect the presence of CAstV antibodies in broilers and sonali chickens (a cross-bread) in Bangladesh through a cross-sectional survey. A total of 454 blood samples from 66 flocks of broiler (n=343) and sonali chickens (n=111) of different ages were obtained during 2017 from four districts. The birds were healthy but were not vaccinated against CAstV. The samples were tested for specific antibodies against CAstV Group B by using commercially available ELISA kit. Overall, 16.74% (76/454) samples and 34.84% (23/66) flocks were positive for CAstV antibodies. The seroprevalence of CAstV was significantly (p=0.001) higher in sonali chickens (36.96%) than broiler (10.20%), while it was significantly higher (p=0.001) in birds of Bogura district (36.94%) than the other three districts. Regarding the age groups, seroprevalence was insignificantly (p=0.192) higher in sonali chicken before laying age (45%) than during laying age (27.45%). Regarding the seasons, CAstV infection was prevalent significantly (p=0.001) higher in winter season. Thus, the present study indicated the presence of CAstV in poultry in Bangladesh, so further studies are required to find out the magnitude of the problem in the country.

scholarly journals Serological surveillance of noroviruses in a community-based prospective cohort: a study protocol

BMJ Open ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. e043228
Author(s):  
Lu Wang ◽  
Dongjie Xie ◽  
Jingrong Yu ◽  
Mark Momoh Koroma ◽  
Mengsi Qiu ◽  
...  
Keyword(s):  
Prospective Cohort ◽  
Herd Immunity ◽  
Age Groups ◽  
Northern China ◽  
Oil Field ◽  
Blood Collection ◽  
Sociodemographic Characteristics ◽  
Blood Group Antigens ◽  
Community Based ◽  
Serological Surveillance

IntroductionNoroviruses are the leading cause of viral acute gastroenteritis affecting all age groups. Since 2014, the previous rarely reported GII.P17-GII.17 and recombinant GII.P16-GII.2 norovirus emerged, replacing GII.4 predominant genotype, causing increased outbreaks in China and other countries. Meanwhile, GII.4/2012 Sydney strain has re-emerged as the dominant variant in many places in 2015–2018. The role of herd immunity as the driving force during these new emerging or re-emerging noroviruses is poorly defined. Serological surveillance studies on community-based prospective cohort on norovirus are highly needed.Methods and analysesThis study will include 1000 out of 9798 participants aged 18 years and above from Caofeidian district, Tangshan city, northern China. Baseline data on sociodemographic characteristics and blood samples were collected in 2013–2014. Blood collection will be replicated annually throughout the cohort until 2023. Saliva samples were also collected in 2016. The seroprevalence and seroincidence of blockade antibodies against norovirus genotypes of GII.P17-GII.17, GII.P16-GII.2, the re-emerged GII.4/2012 and potential novel pandemic variants will be evaluated by ELISA. Associations between genotype blockade antibodies and sociodemographic factors and human histo-blood group antigens will be evaluated using univariate and multivariate analysis. The dynamics of herd immunity duration will be estimated in this longitudinal surveillance.Ethics and disseminationThe study has been approved by the Ethical Committees of the Staff Hospital of Jidong oil-field of China National Petroleum Corporation. This study will provide insight into the seroprevalence and seroincidence of noroviruses, and their relationships with sociodemographic characteristics and genetic susceptibility. It will also explain herd immunity of the emerged and re-emerged genotypes or variants. The study will further enable an understanding of the mechanism driving the replacement of norovirus genotypes. Research findings will be disseminated in peer-reviewed journals and at scientific meetings.

scholarly journals Digital proximity tracing on empirical contact networks for pandemic control

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
G. Cencetti ◽  
G. Santin ◽  
A. Longa ◽  
E. Pigani ◽  
A. Barrat ◽  
...  
Keyword(s):  
Large Scale ◽  
Disease Outbreaks ◽  
Physical Distance ◽  
Contact Tracing ◽  
Reproductive Number ◽  
Modeling Framework ◽  
Infectious Disease Outbreaks ◽  
Contact Patterns ◽  
Contact Data ◽  
The Impact

AbstractDigital contact tracing is a relevant tool to control infectious disease outbreaks, including the COVID-19 epidemic. Early work evaluating digital contact tracing omitted important features and heterogeneities of real-world contact patterns influencing contagion dynamics. We fill this gap with a modeling framework informed by empirical high-resolution contact data to analyze the impact of digital contact tracing in the COVID-19 pandemic. We investigate how well contact tracing apps, coupled with the quarantine of identified contacts, can mitigate the spread in real environments. We find that restrictive policies are more effective in containing the epidemic but come at the cost of unnecessary large-scale quarantines. Policy evaluation through their efficiency and cost results in optimized solutions which only consider contacts longer than 15–20 minutes and closer than 2–3 meters to be at risk. Our results show that isolation and tracing can help control re-emerging outbreaks when some conditions are met: (i) a reduction of the reproductive number through masks and physical distance; (ii) a low-delay isolation of infected individuals; (iii) a high compliance. Finally, we observe the inefficacy of a less privacy-preserving tracing involving second order contacts. Our results may inform digital contact tracing efforts currently being implemented across several countries worldwide.

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