Post-acute COVID and long-COVID among adults and older adults in the State of Paraná, Brazil: protocol for an ambispective cohort study.

introductionSince 2020, the world has been going through a viral pandemic with a high morbidity and mortality rate along with the potential to evolve from an acute infection to post-acute and long-COVID, which is still in the process of elucidation. Diagnostic and prognostic research is essential to understand the complexity of factors and contexts involving the illness's process. This protocol introduces a study strategy to analyse predictors, sequelae, and repercussions of COVID-19 in adults and older adults with different disease severities in the State of Paraná, Brazil. METHODS AND ANALYSIS: A mixed-methods sequential explanatory design. The quantitative data will be conducted by an ambispective cohort study, which will explore the manifestations of COVID-19 for 18 months, with nearly 3000 participants with confirmed diagnoses of COVID-19 (reverse transcription-PCR test) between March and December of 2020, retrieved from national disease reporting databases, over 18 years old, living in a Brazilian State (Paraná) and who survived the viral infection after being discharged from a health service. Data collection will be conducted through telephone interviews, at two different occasions: the first will be a recall 12 months after the acute phase as a retrospective follow-up, and the second will be another prospective interview, with data of the following 6 months. For the qualitative step, Grounded Theory will be used; participants will be selected from the cohort population. The first sample group will be composed of people who were discharged from the intensive care unit, and other sample groups will be composed according to theoretical saturation. The qualitative data will follow the temporal design and classification of the disease provided for in the cohort. ETHICS AND DISSEMINATION: Ethics approval was granted by the State University of Maringá, under opinion number: 4 165 272 and CAAE: 34787020.0.0000.0104 on 21 July 2020, and Hospital do Trabalhador (Worker's Hospital), which is accountable for the Health Department of the State of Paraná, under opinion number: 4 214 589 and CAAE: 34787020.0.3001.5225 on 15 August 2020. The participants will verbally consent to the research, their consent will be recorded, and the informed consent form will be sent by mail or email. Outcomes will be widely disseminated through peer-reviewed manuscripts, conference presentations, media and reports to related authorities.