Modelling the test, trace and quarantine strategy to control the COVID-19 epidemic in the state of São Paulo, Brazil

Amaku, Marcos; Covas, Dimas Tadeu; Coutinho, Francisco Antônio Bezerra; Neto, Raymundo Soares Azevedo; Struchiner, Cláudio J.; Wilder-Smith, Annelies; Massad, Eduardo

doi:10.1016/j.idm.2020.11.004

Cited by 31 publications

(38 citation statements)

References 19 publications

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“…We fitted the model parameters simultaneously to the data of cumulative number of reported cases, deaths and the number of ICU patients (figure9) for the State of Sao Paulo until December 18, 2020. The fitting procedure is described in [16], [17]. To estimate a 95% probability interval (shaded area in figure 9), we assumed a normal distribution for the contact rate with a standard deviation of 1.0%.…”

Section: Resultsmentioning

confidence: 99%

Modelling the Impact of Delaying Vaccination Against SARS-CoV-2 Assuming Unlimited Vaccines Supply

Amaku

Covas

Coutinho

et al. 2021

Preprint

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Background At the moment we have more than 109 million cases and 2.4 million deaths around the world and vaccination represents the only hope to control the pandemic. Imperfections in planning vaccine acquisition and difficulties in implementing distribution among the population, however, have hampered the control of the virus so far. Methods We propose a new mathematical model to estimate the impact of vaccination delay against COVID-19 on the number of cases and deaths by the disease in Brazil. We apply the model to Brazil as a whole and to the State of Sao Paulo, the most affected by COVID-19 in Brazil. We simulated the model for the populations of the State of Sao Paulo and Brazil as a whole, varying the scenarios related to vaccine efficacy and compliance from the populations. Results The model projects that, in the absence of vaccination, almost 170 thousand deaths and more than 350 thousand deaths until the end of 2021 for Sao Paulo and Brazil, respectively. If in contrast, Sao Paulo and Brazil had enough vaccine supply and so started a vaccination campaign in January with the maximum vaccination rate, compliance and efficacy, they could have averted more than 112 thousand deaths and 127 thousand deaths, respectively. In addition, that for each month of delay the number of deaths increases monotonically in a logarithm fashion, for both the State of Sao Paulo and Brazil as a whole. Conclusions Our model shows that the current delay in the vaccination schedules that is observed in many countries has serious consequences in terms of mortality by the disease and should serve as an alert to health authorities to speed the process up such that the highest number of people to be immunized is reached in the shortest period of time.

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Section: Resultsmentioning

confidence: 99%

Modelling the Impact of Delaying Vaccination Against SARS-CoV-2 Assuming Unlimited Vaccines Supply

Amaku

Covas

Coutinho

et al. 2021

Preprint

Self Cite

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“…We modelled the impact of a strategy based on contact tracing of symptomatic individuals on the COVID-19 epidemic in the State of São Paulo, Brazil. This strategy has lower costs when compared to a test-trace-and-quarantine strategy (7). It may be a potential alternative strategy when the number of diagnostic tests available is not sufficient for a massive testing strategy.…”

Section: Discussionmentioning

confidence: 99%

“…The model is based on a modified version of the SEIR model (7,8) and considers that the population at time t is divided into several compartments, namely: susceptible individuals, S ( t ); isolated susceptible individuals, Q S ( t ); susceptible individuals previously isolated,; exposed individuals, E ( t ); asymptomatic/oligosymptomatic individuals, A ( t ); symptomatic individuals, I ( t ); isolated infected individuals, Q ( t ); hospitalized individuals, H ( t ); individuals with severe disease hospitalized in intensive care units (ICU), G ( t ); and recovered individuals, R ( t ).…”

Section: Methodsmentioning

confidence: 99%

“…The model is based on a modified version of the SEIR model (7,8) and considers that the population at time t is divided into several compartments, namely: is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint…”

Section: The Modelmentioning

confidence: 99%

“…The World Health Organization recommends a combination of rapid diagnosis, immediate isolation of cases, rigorous tracking and precautionary self-isolation of close contacts (6). In a previous paper, we analyzed the impact and costs of test-trace-quarantine strategies (7). Here we set out to model the effects of a contact tracing strategy of symptomatic individuals to control the COVID-19 spread regardless of the use of diagnostic testing.…”

Section: Introductionmentioning

confidence: 99%

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Modelling the impact of contact tracing of symptomatic individuals on the COVID-19 epidemic

Amaku

Covas

Coutinho

et al. 2021

Preprint

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OBJECTIVES: With declining numbers of COVID-19 cases in the State of Sao Paulo, Brazil, social distancing measures were gradually being lifted. The risk of an increase in the number of cases, however, cannot be overlooked. Even with the adoption of non-pharmaceutical interventions, such as restrictions on mass gatherings, wearing masks, and complete or partial closure of schools, other public health measures may help to control the epidemic. We aimed to evaluate the impact of the contact tracing of symptomatic individuals on the COVID-19 epidemic regardless of the use of diagnostic testing. METHODS: We developed a mathematical model that includes isolation of symptomatic individuals and tracing of contacts to assess the effects of the contact tracing of symptomatic individuals on the COVID-19 epidemic in the State of Sao Paulo. RESULTS: For a selection efficacy (proportion of isolated contacts who are infected) of 80%, cases and deaths may be reduced by 80% after 60 days when 5000 symptomatic individuals are isolated per day, each of them together with 10 contacts. On the other hand, for a selection efficacy of 20%, the number of cases and deaths may be reduced by approximately 40% and 50%, respectively, compared with the scenario in which no contact tracing strategy is performed. CONCLUSION: Contact tracing of symptomatic individuals may be a potential alternative strategy when the number of diagnostic tests available is not sufficient for a massive testing strategy.

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Effect of Quarantine Strategies in a Compartmental Model with Asymptomatic Groups

et al. 2021

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We present an epidemiological model, which extend the classical SEIR model by accounting for the presence of asymptomatic individuals and the effect of isolation of infected individuals based on testing. Moreover, we introduce two types of home quarantine, namely gradual and abrupt one. We compute the equilibria of the new model and derive its reproduction number. Using numerical simulations we analyze the effect of quarantine and testing on the epidemic dynamic. Given a constraint that limits the maximal number of simultaneous active cases, we demonstrate that the isolation rate, which enforces this constraint, decreases with the increasing testing rate. Our simulations show that massive testing allows to control the infection spread using a much lower isolation rate than in the case of indiscriminate quarantining. Finally, based on the effective reproduction number we suggest a strategy to manage the epidemic. It consists in introducing abrupt quarantine as well as relaxing the quarantine in such a way that the epidemic remains under control and further waves do not occur. We analyze the sensitivity of the model dynamic to the quarantine size, timing and strength of the restrictions.

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Modelling the test, trace and quarantine strategy to control the COVID-19 epidemic in the state of São Paulo, Brazil

Cited by 31 publications

References 19 publications

Modelling the Impact of Delaying Vaccination Against SARS-CoV-2 Assuming Unlimited Vaccines Supply

Modelling the Impact of Delaying Vaccination Against SARS-CoV-2 Assuming Unlimited Vaccines Supply

Modelling the impact of contact tracing of symptomatic individuals on the COVID-19 epidemic

Effect of Quarantine Strategies in a Compartmental Model with Asymptomatic Groups

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