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

Abstract

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.

Importance of epidemic severity and vaccine mode of action and availability for delaying the second vaccine dose

“…Even so, while everything sounded promising during the autumn 2020 months, delays and shortages in vaccine supplies in spring 2021 led to complications and spurred thinking on strategies that would speed up vaccination, despite limited vaccine supplies. Indeed, models have clearly demonstrated that vaccine deployment delays substantially affected the course of the pandemic (3,4). Eventually, the strategy of delaying the second dose, required for all actually available vaccines except the Janssen one produced by Johnson & Johnson (5), has often been adopted.…”

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

“…We fitted the model parameters simultaneously to the data of cumulative number of reported cases and deaths(figure3(a)) for Brazil and to the data of cumulative number of reported cases, deaths and the number of intensive care units (ICU) patients (figure3(b)) for the State of Sao Paulo until December 18, 2020. The fitting procedure is described in[18][19][20].…”