ObjectivesThe National Vaccination Plan against SARS-CoV-2/COVID-19 was launched by the Ministry of Health and Social Protection, on 14 February 2021. The main objective of the study was to evaluate the effectiveness of the Corona Vac in preventing three clinical outcomes defined as Infection, Hospitalisation or Death, in a real-world scenario.DesignThis is a population-based retrospective dynamic cohort study using a multivariate Cox model to calculate Hazard Ratios (HR) for estimate of vaccine effectiveness, starting on 17 Feb 2021 up to 30 June 2022. The data were taken from the surveillance systems for 12 months for each individual. Four cities were selected considering that each one had a reliable data base.ResultsCorona Vac effectiveness was estimated in 32% (95% CI 31-33) in preventing infection, 55% (95%CI 54-56) in hospitalisation, and 90% (95%CI 89-90) in death, at the end of the follow-up. These findings were more consistent during the four first months. Comparing with unvaccinated, booster homologous doses did appear to increase effectiveness in preventing hospitalisation, but for booster heterologous increase protection for hospitalisation and death. Booster doses to whom already were vaccinated with CoronaVac did not improve its effectiveness neither when they received heterologous boosters.ConclusionsCoronaVac shows effectiveness in preventing death or hospitalisation during the first year of follow-up, but less in preventing infection, decreasing rapidly after the first four months of follow-up. It was higher in children between 3 and 12 years, as well as in those over 60. Boosters' doses did not improved effectiveness in those CoronaVac already vaccinated.