2.1. Study Design and Data Sources

A retrospective cohort study was conducted in health workers from 9 February to 26 June 2021, using secondary information from databases of the Ministry of Health that included demographic, epidemiological, clinical, hospital data, data from the laboratory (polymerase chain reaction test (PCR) and antigenic tests for the detection of SARS-CoV-2), death, as well as both the date and quantity of vaccination doses against SARS-CoV-2.

The integrated database was built from the amalgamation of the following data sources: the national vaccination registry of the General Office of Information Technology; the National Registry of Health Personnel; Smart Health System (ESSI) records of the Social Health Insurance of Peru; records of the Comprehensive Health Insurance (SIS); records from the Integrated System for COVID-19; clinical and laboratory data for SARS-CoV-2 from the laboratory information system (NetLab v2.0) of the National Institute of Health (NIH); and the information system of the epidemiological surveillance of COVID-19 of the National Center of Epidemiology, Prevention and Control of Diseases of Peru. The information on COVID 19-related deaths was obtained from the National Informatic System of Defunctions of the General Office of Information Technology. The type of profession was identified from the database of eleven professional associations in Peru.

The General Office of Information Technology of the Ministry of Health joined the different databases, providing the researchers with identification data of the anonymized subjects and the study’s variables of interest. The quality control of the data was performed by the institution responsible for the database, the General Office of Information Technology, and the researchers.