COVID-19 pandemic has increased inequalities in almost every aspect of human life: access to health care, education, jobs, income, and technologies such as vaccines or digital resources. Socially vulnerable populations have been significantly affected by the pandemic, reflecting in higher COVID-19 rates, increased poverty and food insecurity. We elaborated a comparative before-and-after evaluation design from March, 2020 to April, 2021 in Complexo da Maré community, a large vulnerable favela in Rio de Janeiro, Brazil. Our objective was to analyze the impact of a multicomponent intervention that combines community engagement strategies, mobile surveillance, testing, and telehealth in order to detect cases and reduce mortality of COVID-19. We performed a two-fold analysis to estimate the intervention effect on the progression of cases and deaths in Maré. Firstly compared the COVID-19 rates reported in Maré, the intervention group, to three communities in Rio de Janeiro jointly as the control group - Rocinha, Cidade de Deus, and Mangueira. Secondly, we conducted a Difference-in-Difference (DID) analysis. Before the intervention, Maré had presented lower rates of COVID-19 cases than the control group and the Rio de Janeiro municipality. Although the number of reported deaths in Maré was comparable to the control group, Maré had displayed a higher case-fatality ratio in this prior period. After the intervention onset, Maré reported cases were two times higher than the control group and the municipality. In contrast, the reported death rates decreased by half in Maré after the intervention (-60 per cent), whereas the rate reduction was significantly lower in the control group (-28 per cent). Considering the intervention effect compared to the control group, we observed an increase of the reported cases per week (26 cent, 95 cent CI: 24 per cent -27 per cent), and a decrease of the reported death rates per week (-48 per cent, 95 cent CI: 46 per cent -50 per cent). In conclusion, the integrated model of health surveillance to support Rio de Janeiro s favelas during the pandemic was considered capable of preventing and controlling virus transmission. In this regard, the initiative helped to guarantee social protection for a vulnerable population and to develop effective prevention mechanisms.