Effectiveness of the 2023-2024 Omicron XBB.1.5-containing mRNA COVID-19 vaccine (mRNA-1273.815) in preventing COVID-19-related hospitalizations and medical encounters among adults in the United States: An interim analysis (preprint)

Background/ObjectivesCOVID-19 continues to pose a significant burden that impacts public health and the healthcare system as the SARS-CoV-2 virus continues to evolve. Regularly updated vaccines are anticipated to boost waning immunity and provide protection against circulating variants. This study evaluated vaccine effectiveness (VE) of mRNA-1273.815, a 2023-2024 Omicron XBB.1.5-containing mRNA COVID-19 vaccine, at preventing COVID-19-related hospitalizations and any medically attended COVID-19 in adults [≥]18 years, overall, and by age and underlying medical conditions. MethodsThis retrospective cohort study used the Veradigm Network EHR linked to claims data to identify US adults [≥]18 years of age who received the mRNA-1273.815 vaccine (exposed) matched 1:1 to individuals who did not receive a 2023-2024 updated COVID-19 vaccine (unexposed). Patients in the unexposed cohort were randomly matched to eligible mRNA-1273.815 recipients. Inverse probability of treatment weighting was used to adjust for differences between the two cohorts. The exposed cohort was vaccinated between September 12, 2023, and December 15, 2023, and individuals in both cohorts were followed up for COVID-19-related hospitalizations and medically attended COVID-19 until December 31, 2023. A Cox regression model was used to estimate the hazard ratio (HR). VE of the mRNA-1273.815 vaccine in preventing COVID-19-related hospitalizations and any medically attended COVID-19 was estimated as 100*(1-HR). Subgroup analyses were performed for adults [≥]50, adults [≥]65, and individuals with underlying medical conditions associated with severe COVID-19 outcomes. ResultsOverall, 859,335 matched pairs of mRNA-1273.815 recipients and unexposed adults were identified. The mean age was 63 years, and 80% of the study population was [≥]50 years old. 61.5% of the mRNA-1273.815 cohort and 66.4% of the unexposed cohort had an underlying medical condition. Among the overall adult population ([≥]18 years), VE was 60.2% (53.4-66.0%) against COVID-19-related hospitalization and 33.1% (30.2%-35.9%) against medically attended COVID-19 over a median follow-up of 63 (IQR: 44-78) days. VE estimates by age and underlying medical conditions were similar. ConclusionsThese results demonstrate the significant protection provided by mRNA-1273.815 against COVID-19-related hospitalizations and any medically attended COVID-19 in adults 18 years and older, regardless of their vaccination history, and support CDC recommendations for vaccination with the 2023-2024 Omicron XBB.1.5-containing COVID-19 vaccine to prevent COVID-19-related outcomes, including hospitalizations.

Comparative Effectiveness of the Bivalent (Original/Omicron BA.4/BA.5) mRNA COVID-19 Vaccines mRNA-1273.222 and BNT162b2 Bivalent in Adults in the United States (preprint)

Background: The emergence of Omicron variants coincided with declining vaccine-induced protection against SARS-CoV-2 infection and other COVID-19-related outcomes. Two bivalent mRNA vaccines, mRNA-1273.222 (Moderna) and BNT162b2 Bivalent (Pfizer-BioNTech) were developed to provide greater protection against the predominate circulating variants by including the mRNA that encodes both the ancestral (original) strain and BA.4/BA.5. We estimated their relative vaccine effectiveness (rVE) in preventing COVID-19-related outcomes in the US. Methods: We conducted a retrospective cohort study using a US nationwide dataset linking primary care electronic health records (EHR) and pharmacy/medical claims data. The adult study population (aged >18 years) received either mRNA-1273.222 or BNT162b2 Bivalent vaccination between August 31, 2022, and February 28, 2023. We used a propensity score weighting based on the inverse probability of treatment to adjust for the baseline differences in age, sex, race, ethnicity, geographic region, vaccination week, and health status between groups. Outcomes evaluated were rVE of the two bivalent mRNA vaccines against COVID-19-related hospitalizations (primary outcome) and outpatient visits (secondary). We weighted the vaccine groups prior to analysis and estimated adjusted hazard ratios (HR) using multivariable Cox regression models. We calculated rVE as (1-HR) X 100. Results: We evaluated outcomes for 1,034,538 mRNA-1273.222 and 1,670,666 BNT162b2 Bivalent vaccine recipients. The adjusted rVE of mRNA-1273.222 versus BNT162b2 Bivalent vaccines against COVID-19-related hospitalization was 9.8% (95% confidence interval: 2.6% --16.4%). The adjusted rVE against COVID-19-related outpatient visits was 5.1% (95% CI: 3.2% --6.9%). When evaluated by age group, the incremental relative effectiveness was greater. Among adults [≥]65, rVE against COVID-19-related hospitalizations and outpatient visits was 13.5% (95% CI: 5.5% -- 20.8%) and 10.7% (8.2% -- 13.1%), respectively. Conclusion: We found greater effectiveness of mRNA-1273.222 compared with the BNT162b2 Bivalent vaccine in preventing COVID-19-related hospitalizations and outpatient visits, with increased benefits in older adults

Change in childbearing intention, use of contraception, unwanted pregnancies, and related adverse events during the COVID-19 pandemic: Results from a panel study in rural Burkina Faso

Evidence on how the COVID-19 pandemic has affected women's reproductive health remains scarce, particularly for low- and middle-income countries. Deleterious indirect effects seem likely, particularly on access to contraception and risk of unwanted pregnancies, but rigorous evaluations using quasi-experimental designs are lacking. Taking a diachronic perspective, we aimed to investigate the effects of the pandemic on four indicators of women's reproductive health: history of recent adverse events during pregnancy (past), use of contraception and unwanted pregnancies (present), and childbearing intentions (future). This study was conducted in four rural health districts of Burkina Faso: Banfora, Leo, Sindou and Tenado. Two rounds of household surveys (before and during the pandemic) were conducted in a panel of 696 households using standardized questionnaires. The households were selected using a stratified two-stage random sampling method. All women aged 15–49 years living in the household were eligible for the study. The same households were visited twice, in February 2020 and February 2021. The effects were estimated by fitting hierarchical regression models with fixed effects or random intercepts at the individual level. A total of 814 and 597 women reported being sexually active before and during the COVID-19 pandemic, respectively. The odds of not wanting (any more) children were two times higher during the pandemic than before (2.0, 95% CI [1.32–3.04]). Among those with childbearing intention, the average desired delay until the next pregnancy increased from 28.7 to 32.8 months. When comparing 2021 versus 2020, there was an increase in the adjusted odds ratio of contraception use (1.23, 95% CI [1.08–1.40]), unwanted pregnancies (2.07, 95% CI [1.01–4.25]), and self-reported history of miscarriages, abortions, or stillbirths in the previous 12 months (2.4, 95% CI [1.04–5.43]). Our findings in rural Burkina Faso do not support the predicted detrimental effects of COVID-19 on the use of family planning services in LMICs, but confirm that it negatively affects pregnancy intentions. Use of contraception increased significantly among women in the panel, but arguably not enough to avoid an increase in unwanted pregnancies.

Causes of higher levels of stress among students in higher education who used eLearning platforms during the COVID-19 pandemic.

Background: This work aims to study the levels of stress among students using e-learning platforms during the COVID-19 pandemic in higher education institutions. The major factors of higher-level stress among the student community focused on this study are: Changes in academic environment, family, social, personal, health and cognitive. Objective: the objective of this research the Partial Least Squares Structural Equation Modelling (PLS-SEM) procedure was used to explore the relationship and its impact on various levels of stress. Results: Data were collected by using a total of 1,000 email IDs of students that were made available by teachers from 12 Indian higher education institutions where they were enrolled and by using a random number method. With this procedure, a total of 800 email IDs were selected. The results drawn from this research are that students experienced more stress due to sudden changes in the academic environment, family, and personal factors. The stress levels of cognitive and social were found to be equally distributed among higher education students, but less than academic environment, family and personal. This research intends to fill the gap of short-term individual psychological changes that occur after the outbreak. Conclusion: Policy-makers can take note of the current study's observations in continuing their fight against COVID-19 pandemic by improving the stability for student risk groups.

Post-COVID-19 syndrome and insulin resistance 20 months after a mild COVID-19 (preprint)

Objective SARS-CoV-2 infection is associated with impaired glucose metabolism. Although the mechanisms are not fully understood, insulin resistance (IR) appears to be a central factor. Patients who had a severe acute phase, but even asymptomatic or with mild COVID-19, have an increased risk of T2DM. After the acute phase, post-COVID-19 syndrome (PCS) also seems to be related to this metabolic disturbance, but there is a paucity of studies. This study aims to evaluate a possible relationship between PCS and IR after mild COVID-19 and, if confirmed, whether there are differences by sex. Subjects and methods Retrospective observational cohort study including subjects who had mild COVID-19 between April and September 2020 in a community setting. None had been vaccinated against SARS-CoV-2 at inclusion, and previous T2DM and liver disease were exclusion criteria. Patients who met NICE criteria were classified as PCS+. Epidemiological and laboratory data were analysed. Three assessments were performed: 1E (pre-COVID-19, considered baseline and reference for comparisons), 2E (approximately 3 months after the acute phase), and 3E (approximately 20 months after the acute phase). A triglyceride-to-glucose (TyG) index [≥]8.74 was considered IR. Albumin-to-globulin ratio (AGR) and lactate dehydrogenase (LDH) were assessed as inflammatory markers. Bivariate analyses were performed, using nonparametric and repeated measures tests. A subsample without metabolic disorder or CVD (age< median, BMI<25 kg/m^2, elevated AGR, TyG index=7.80 [0.5]) was generated to reasonably rule out prior baseline IR that could bias the results. The relationships between PCS and TyG in 3E (TyG3) were modeled in 8 multiple regressions, stratifying by sex and BMI combinations. Results A total of 112 subjects (median [IQR] of age= 44 [20] years; 65 women) were analysed. Up to 14.3% was obese and 17% was hypertensive. Significant increases between 1E and 3E were registered regarding (i) basal glycemia (BG), 87 [14] mg/dL vs. 89 [14]; p=0.014, (ii) TyG index (8.25 [0.8] vs. 8.32 [0.7]; p=0.002), and (iii) LDH in 3rd tertile (16.1% vs 32.1%; p=0.007). A total of 8 previously normoglycemic subjects, showed BG2 or BG3 >126 mg/dL. The subgroups with IR highest prevalence at 3E were those of BMI [≥]25 kg/m^2 and PCS+. The subgroup without CVD presented a significant increase in the TyG index (TyG1=7.80 [0.1] vs. TyG3= 8.28 [0.1]; p=0.017). LDH1 was significantly correlated with TyG3 in both sexes (rho=0.214 in women, rho=0.298 in men); in contrast, LDH2 and LDH3 did not present such an association. In multivariable analysis, PCS has shown to be an independent and predictive variable of TyG index in women with BMI<25 kg/m^2, after adjustment for age, hypertension, BMI, Charlson comorbidity index, AGR1, AGR2, LDH1, number of symptoms of acute COVID-19, and number of days of the acute episode (beta coefficient=0.350; p=0.039). Conclusions PCS has played a secondary role in predicting IR, showing a modest effect compared to BMI or prior hypertension. A significant increase in IR has been noted 20 months after mild COVID-19, both in cases of previous baseline IR and in those without previous IR. Basal serum LDH has shown to be predictive of current TyG, regardless of elevated LDH after SARS-CoV-2 infection. There were profound differences between women and men, confirming the need for a sex-stratified analysis when addressing the relation between PCS and glycemic alterations.

Relative effectiveness of BNT162b2, mRNA-1273, and Ad26.COV2.S vaccines and homologous boosting in preventing COVID-19 in adults in the US (preprint)

Background: Few head-to-head comparisons have been performed on the real-world effectiveness of COVID-19 booster vaccines. We evaluated the relative effectiveness (rVE) of a primary series of mRNA-1273 versus BNT162b2 and Ad26.COV2.S and a homologous mRNA booster against medically-attended, outpatient, and hospitalized COVID-19. Methods: A dataset linking primary care electronic medical records with medical claims data was used for this retrospective cohort study of US patients [≥]18 years vaccinated with a primary series between February and October 2021 (Part 1) and a homologous mRNA booster between October 2021 and January 2022 (Part 2). Adjusted hazard ratios (HR) were derived from 1:1 matching adjusted across potential covariates. rVE was (1-HRadjusted) x 100. Additional analysis was performed across regions and age groups. Results: Following adjustment, Part 1 rVE for mRNA-1273 versus BNT162b2 was 23% (95% CI: 22%-25%), 23% (22%-25%), and 19% (14%-24%) whilst the rVE for mRNA-1273 versus Ad26.COV2.S was 50% (48%-51%), 50% (48%-52%), and 57% (53%-61%) against any medically-attended, outpatient, and hospitalized COVID-19, respectively. The adjusted rVE in Part 2 for mRNA-1273 versus BNT162b2 was 14% (10%-18%), 13% (8%-17%), and 19% (1%-34%) against any medically-attended, outpatient, and hospitalized COVID-19, respectively. rVE against medically-attended COVID-19 was higher in adults [≥]65 years (35%; 24%-47%) than those 18-64 years (13%; 9%-17%) after the booster. Conclusions: In this study, mRNA-1273 was more effective than BNT162b2 or Ad26.COV2.S following primary series during a Delta-dominant period, and than BNT162b2 as a booster during an Omicron-dominant period.

It takes a pirate to know one: ethical hackers for healthcare cybersecurity.

Healthcare cybersecurity is increasingly targeted by malicious hackers. This sector has many vulnerabilities and health data is very sensitive and valuable. Consequently, any damage caused by malicious intrusions is particularly alarming. The consequences of these attacks can be enormous and endanger patient care. Amongst the already-implemented cybersecurity measures and the ones that need to be further improved, this paper aims to demonstrate how penetration tests can greatly benefit healthcare cybersecurity. It is already proven that this approach has enforced cybersecurity in other sectors. However, it is not popular in healthcare since many prejudices still surround the hacking practice and there is a lack of education on hackers' categories and their ethics. The present analysis aims to comprehend what hacker ethics is and who ethical hackers are. Currently, hacker ethics has the status of personal ethics; however, to employ penetration testers in healthcare, it is recommended to draft an official code of ethics, comprising principles, standards, expectations, and best practices. Additionally, it is important to distinguish between malicious hackers and ethical hackers. Amongst the latter, penetration testers are only a sub-category. Acknowledging the subtle differences between ethical hackers and penetration testers allows to better understand why and how the latter can offer their services to healthcare facilities.

The unequal effects of the health-economy tradeoff during the COVID-19 pandemic (preprint)

The potential tradeoff between health outcomes and economic impact has been a major challenge in the policy making process during the COVID-19 pandemic. Epidemic-economic models designed to address this issue are either too aggregate to consider heterogeneous outcomes across socio-economic groups, or, when sufficiently fine-grained, not well grounded by empirical data. To fill this gap, we introduce a data-driven, granular, agent-based model that simulates epidemic and economic outcomes across industries, occupations, and income levels with geographic realism. The key mechanism coupling the epidemic and economic modules is the reduction in consumption demand due to fear of infection. We calibrate the model to the first wave of COVID-19 in the New York metropolitan area, showing that it reproduces key epidemic and economic statistics, and then examine counterfactual scenarios. We find that: (a) both high fear of infection and strict restrictions similarly harm the economy but reduce infections; (b) low-income workers bear the brunt of both the economic and epidemic harm; (c) closing non-customer-facing industries such as manufacturing and construction only marginally reduces the death toll while considerably increasing unemployment; and (d) delaying the start of protective measures does little to help the economy and worsens epidemic outcomes in all scenarios. We anticipate that our model will help designing effective and equitable non-pharmaceutical interventions that minimize disruptions in the face of a novel pandemic.

Antibiotic Resistance in Respiratory Bacterial Isolates From Critical Care Patients Infected With Sars-CoV2 (preprint)

Purpose: . Although secondary bacterial infections are uncommon in COVID-19, ventilator pneumonia is a hazard. We undertook a retrospective, observational study at an ICU in Vicenza, Italy, comparing pulmonary bacterial isolates between COVID-19 and non-COVID-19 patients. Methods: . Respiratory bacteria were recovered from: (i) ICU patients admitted in Feb-May 2019, pre-pandemic; (ii) ICU patients admitted with COVID-19 during the first (Feb-May 2020) wave and (iii) non-COVID-19 ICU patients from Feb-May 2020. Results: . We reviewed 120 patients, 61 in the control (2019) group and 59 (28 COVID-19 and 31 non-COVID-19) from 2020. Two hundred isolates were grown: 101 from the 2019 control patients, 42 from the 2020 COVID-19 patients and 57 from the 2020 non-COVID patients. Enterobacterales dominated throughout but Pseudomonas aeruginosa was significantly (p <0.01) more prevalent in COVID-19 than non-COVID patients and MDR P. aeruginosa (3/12; 25%) were exclusively found in COVID-19 patients. Other critical resistance types (MRSA, ESBL- and carbapenemase-producing Enterobacterales ) were rare, without significant differences in prevalence between groups. ICU and hospital mortality were greater among COVID-19 than non-COVID patients. Deaths occurred in 6/9 COVID patients (66.7%) who did not receive targeted antibiotic therapy despite microbiological diagnosis. Conclusion: . These data underscore the importance of secondary bacterial pathogens in ICU COVID patients and the threat of antibiotic inadequacy favouring poor outcomes in VAP. The organisms found in COVID patients were typical of VAP, though P. aeruginosa was more prominent.

Change in childbearing intention, use of contraception, unwanted pregnancies, and related adverse events during the COVID-19 pandemic: Results from a panel study in rural Burkina Faso.

Evidence on how the COVID-19 pandemic has affected women's reproductive health remains scarce, particularly for low- and middle-income countries. Deleterious indirect effects seem likely, particularly on access to contraception and risk of unwanted pregnancies, but rigorous evaluations using quasi-experimental designs are lacking. Taking a diachronic perspective, we aimed to investigate the effects of the pandemic on four indicators of women's reproductive health: history of recent adverse events during pregnancy (past), use of contraception and unwanted pregnancies (present), and childbearing intentions (future). This study was conducted in four rural health districts of Burkina Faso: Banfora, Leo, Sindou and Tenado. Two rounds of household surveys (before and during the pandemic) were conducted in a panel of 696 households using standardized questionnaires. The households were selected using a stratified two-stage random sampling method. All women aged 15-49 years living in the household were eligible for the study. The same households were visited twice, in February 2020 and February 2021. The effects were estimated by fitting hierarchical regression models with fixed effects or random intercepts at the individual level. A total of 814 and 597 women reported being sexually active before and during the COVID-19 pandemic, respectively. The odds of not wanting (any more) children were two times higher during the pandemic than before (2.0, 95% CI [1.32-3.04]). Among those with childbearing intention, the average desired delay until the next pregnancy increased from 28.7 to 32.8 months. When comparing 2021 versus 2020, there was an increase in the adjusted odds ratio of contraception use (1.23, 95% CI [1.08-1.40]), unwanted pregnancies (2.07, 95% CI [1.01-4.25]), and self-reported history of miscarriages, abortions, or stillbirths in the previous 12 months (2.4, 95% CI [1.04-5.43]). Our findings in rural Burkina Faso do not support the predicted detrimental effects of COVID-19 on the use of family planning services in LMICs, but confirm that it negatively affects pregnancy intentions. Use of contraception increased significantly among women in the panel, but arguably not enough to avoid an increase in unwanted pregnancies.

Real-world comparative effectiveness of mRNA-1273 and BNT162b2 vaccines among immunocompromised adults in the United States (preprint)

Introduction: Head-to-head studies comparing COVID-19 mRNA vaccine effectiveness in immunocompromised individuals, who are vulnerable to severe disease are lacking, as large sample sizes are required to make meaningful inferences. Methods: This observational comparative effectiveness study was conducted in closed administrative claims data from the US HealthVerity database (December 11, 2020-January 10, 2022, before omicron). A 2-dose mRNA-1273 versus BNT162b2 regimen was assessed for preventing medically-attended breakthrough COVID-19 diagnosis and hospitalizations among immunocompromised adults. Inverse probability of treatment weighting was applied to balance baseline characteristics between vaccine groups. Incidence rates from patient-level data and hazard ratios (HRs) using weighted Cox proportional hazards models were calculated. Results: Overall, 57,898 and 66,981 individuals received a 2-dose regimen of mRNA-1273 or BNT161b2, respectively. Among the weighted population, mean age was 51 years, 53% were female, and baseline immunodeficiencies included prior blood transplant (8%-9%), prior organ transplant (7%), active cancer (12%-13%), primary immunodeficiency (25%-26%), HIV (20%-21%), and immunosuppressive therapy use (60%-61%). Rates per 1,000 person-years (PYs; 95% confidence intervals [CI]s) of breakthrough medically-attended COVID-19 were 25.82 (23.83-27.97) with mRNA-1273 and 30.98 (28.93, 33.18) with BNT162b2 (HR, 0.83; 95% CI, 0.75-0.93). When requiring evidence of an antigen or polymerase chain reaction test before COVID-19 diagnosis, the HR for medically-attended COVID-19 was 0.78 (0.67-0.92). Breakthrough COVID-19 hospitalization rates per 1,000 PYs (95% CI) were 3.66 (2.96-4.51) for mRNA-1273 and 4.68 (3.91-5.59) for BNT162b2 (HR, 0.78; 0.59-1.03). Utilizing open and closed claims for outcome capture only, or both cohort entry/outcome capture, produced HRs (95% CIs) for COVID-19 hospitalization of 0.72 (0.57-0.92) and 0.66 (0.58-0.76), respectively. Conclusions: Among immunocompromised adults, a 2-dose mRNA-1273 regimen was more effective in preventing medically-attended COVID-19 in any setting (inpatient and outpatient) than 2-dose BNT162b2. Results were similar for COVID-19 hospitalization, although statistical power was limited when using closed claims only. Study Registration: NCT05366322

Impact of COVID‐19 on glycaemic control in a Spanish cohort of patients with type 2 diabetes

The purpose of this study was to investigate the impact of COVID‐19 lockdown on monitoring and glycaemic control of people with type 2 diabetes (T2DM) in a Spanish population.This prospective cohort study focused on patients with T2DM from a Spanish cohort followed since 2017, with at least one HbA1c determination since the start of the pandemic.A total of 246 patients was included;45.9% (113) had at least one HbA1c measurement during the pandemic and, in this case, we used the most recent one. The HbA1c mean value increased from 7.37% before the pandemic to 7.43% (p = 0.63). Those patients with previous HbA1c ≥ 8.5% were the ones whose glycaemic controlled worsened: uncontrolled patients increased from 10.5% to 28.6% (p < 0.05), relative risk 1.65.In conclusion, nine months after the pandemic start, less than a half of the T2DM patients in our Spanish cohort had at least one HbA1c measurement. Glycaemic control was similar when comparing before versus after the pandemic start, although those patients who were previously poorly controlled had a 1.65 higher risk of worsening their glycaemic control compared to the rest. Copyright © 2022 John Wiley & Sons.

Quantifying the importance and location of SARS-CoV-2 transmission events in large metropolitan areas (preprint)

Detailed characterization of SARS-CoV-2 transmission across different settings can help design less disruptive interventions. We used real-time, privacy-enhanced mobility data in the New York City and Seattle metropolitan areas to build a detailed agent-based model of SARS-CoV-2 infection to estimate the where, when, and magnitude of transmission events during the pandemics first wave. We estimate that only 18% of individuals produce most infections (80%), with about 10% of events that can be considered super-spreading events (SSEs). Although mass-gatherings present an important risk for SSEs, we estimate that the bulk of transmission occurred in smaller events in settings like workplaces, grocery stores, or food venues. The places most important for transmission change during the pandemic and are different across cities, signaling the large underlying behavioral component underneath them. Our modeling complements case studies and epidemiological data and indicates that real-time tracking of transmission events could help evaluate and define targeted mitigation policies.

Modeling the impact of social distancing, testing, contact tracing and household quarantine on second-wave scenarios of the COVID-19 epidemic (preprint)

The new coronavirus disease 2019 (COVID-19) has required the implementation of severe mobility restrictions and social distancing measures worldwide. While these measures have been proven effective in abating the epidemic in several countries, it is important to estimate the effectiveness of testing and tracing strategies to avoid a potential second wave of the COVID-19 epidemic. We integrate highly detailed (anonymized, privacy-enhanced) mobility data from mobile devices, with census and demographic data to build a detailed agent-based model to describe the transmission dynamics of SARS-CoV-2 in the Boston metropolitan area. We find that enforcing strict social distancing followed by a policy based on a robust level of testing, contact-tracing and household quarantine, could keep the disease at a level that does not exceed the capacity of the health care system. Assuming the identification of 50% of the symptomatic infections, and the tracing of 40% of their contacts and households, which corresponds to about 9% of individuals quarantined, the ensuing reduction in transmission allows the reopening of economic activities while attaining a manageable impact on the health care system. Our results show that a response system based on enhanced testing and contact tracing can play a major role in relaxing social distancing interventions in the absence of herd immunity against SARS-CoV-2.