Available online at www.SciMedJournal.org SciMedicine Journal (ISSN: 2704-9833) Vol. 3, Special Issue "COVID-19", 2021 80 Second Wave Analysis and Confirmed Forecasts of the SARS-Cov-2 Epidemic Outbreak in São Paulo, Brazil Sergio Celaschi 1* 1 CTI Renato Archer, Rod. D Pedro I (SP-65), Km 143,6 - CEP 13069-901, Campinas – SP, 13069, Brazil. Received 15 March 2021; Revised 26 May 2021; Accepted 08 June 2021; Published 21 June 2021 Abstract Objective: A SEIR compartmental model was previously selected to estimate future outcomes to the dynamics of the Covid-19 epidemic breakout in Brazil. Method: Compartments for individuals vaccinated and prevalent SARS-Cov-2 variants were not included. A time-dependent incidence weight on the reproductive basic number accounted for Non Pharmaceutical Interventions (NPI). A first series of published data from March 1 st to May 8, 2020 was used to adjust all model parameters aiming to forecast one year of evolutionary outbreak. The cohort study was set as a city population- based analysis. Analysis: A population-based sample of 25,366 confirmed cases on exposed individuals was used during the first study period. The analysis was applied to predict the consequences of NPI enforcements followed by progressive releases, and indicates the appearance of a second wave starting last quarter of 2020. Findings: By March 1 st 2021, the number of confirmed cases was predicted to reach 0.47Million (0.24-0.78), and fatalities would account for 21 thousand (12-33), 5 to 95% CRI. A second series of data published from May 9, 2020 to March 1 st , 2021 confirms the forecasts previously reported for the evolution of infected people and fatalities. Novelty: By March 1 st 2021, the number of confirmed cases reached 527,710 (12% above the predicted average of accumulated cases) and fatalities accounted for 18,769 (10% below the accumulated average of estimated fatalities). After March 1 st , new peaks on reported numbers of daily new infected and new fatalities appeared as a combined result to the appearance of the prevalent SARS-CoV-2 P1 variant, and the increased number of vaccinated individuals. Keywords: COVID-19; Brazil; Confirmed Forecast; NPI and Mitigation Policy; Second Wave; Prevalent Variants; Vaccination. 1. Introduction COVID-19 was first reported in Brazil in February 2020 and one semester later, the country became one of the worst affected globally. After six months from the first reported case, the number of confirmed cases and deaths surpassed 3.9 million and 120 thousand, respectively; facts that question the availability of public health care for a major fraction of society [1, 2]. Since October 2020, all parts of the world were impacted by the COVID-19 epidemic, with more than 40 million cases and 1.1 million deaths reported [3]. This work aims to confirm previous forecasts reported on May, 2020 [4] for the COVID-19 epidemic expansion of in S. Paulo, the most populated Brazilian city with its 12.2 million inhabitants. This city was selected once the first positive tested patient in Brazil was there. Since then, by April 25 2021, were officially confirmed in Brazil 14.4 million cases with 391 thousand deaths and in S. Paulo city 704,989 cases and 26,642 deaths. Before the beginning of vaccination, the worldwide response to the pandemic has been the introduction of Non Pharmaceutical Interventions (NPIs) as mitigation policies. * Corresponding author: sergio.celaschi@cti.gov.br http://dx.doi.org/10.28991/SciMedJ-2021-03-SI-10  This is an open access article under the CC-BY license (https://creativecommons.org/licenses/by/4.0/). © Authors retain all copyrights.