Local protection bubbles: an interpretation of the decrease in the velocity of coronavirus's spread in the city of Sao Paulo

After four months of dealing with the pandemic, the city of São Paulo entered a phase of relaxed social-distancing measures in July 2020, and saw its social isolation rate fall at the same time as the number of cases, deaths, and hospital bed occupation declined. We use a calibrated multi-agent model to describe these dynamics. We assert here that this phenomenon can be understood as the result of local protective bubbles formed in the city’s sub-environments at the same time that there was an exhaustion of contagion networks. Both reduce the velocity of the virus’s spread, causing temporary reductions in the epidemic curve, albeit in an unstable equilibrium. These local bubbles can burst anytime and anywhere due to the reintroduction of a few infected people at the same time that there is a reduction in non-pharmaceutical interventions (NPI), such as social-distancing practices. It is important to stress that this hypothesis aligns with the dynamics of the virus’s spread observed so far, without needing ad hoc suppositions about natural collective immunity thresholds or heterogeneity in the population’s transmission rate, which come with the risk of making mistaken predictions that may could lead to the loss of many lives. The safe way to move ahead is to continue doing all we can to avoid new infections until a vaccine is found that properly and safely creates herd immunity. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by Tide Setubal Foundation and the Federal University of ABC. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Although this research used some literature data as inputs to the model, such as the incubation period, which is human, data from clinical or laboratory exams of patients were not used. Therefore, it is exempt from the appraisal of a research ethics committee by the Brazilian legislation expressed in the Resolution of the National Health Council (CONEP) number 466/12. All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes I declare that all data referred to in the manuscript is available