Severe Acute Respiratory Syndrome Coronavirus 2 Re-Infection Risk and Vaccine Efficacy in Austria

The coronavirus disease 2019 (COVID-19) pandemic was caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. In this study, we aim to evaluate how strong and how long are individuals in Austria after vaccination and/or infection with SARS-CoV-2 protected against COVID-19 disease.

In this project, we will analyze national health data from all inhabitants of Austria (about 9 million persons) during the COVID-19 pandemic. The population of Austria will be stratified into different groups according to previous vaccinations against SARS-CoV-2 and previous SARS-CoV-2 infections.

We primarily evaluate how strong and how long after vaccination against SARS-CoV-2 and/or infection with SARS-CoV-2, the risk for COVID-19 deaths is reduced or altered as compared to less vaccinated and/or infected persons. As secondary study aims, we perform such analyses also for SARS-CoV-2 infections, hospitalizations and intensive care unit (ICU) stays, with or due to SARS-CoV-2. These analyses will be performed during different time periods of the COVID-19 pandemic, and we will also perform various subgroup analyses as for example according to age and gender. Given that antibodies against SARS-CoV-2 are usually detected after vaccination and/or infection, we will use such antibody data from blood donors in Tyrol, to elucidate how well the national health data on SARS-CoV-2 infections and vaccinations match with the respective antibody data, and how well these antibody data indicate risk of COVID-19 deaths and infections.

We will calculate the probability of dying due to a SARS-CoV-2 infection (case/infection fatality rate) for different times of the COVID-19 pandemic, in order to document the health threat due to SARS-CoV-2. Based on all these data, we will calculate how many persons have to be vaccinated against SARS-CoV-2 to prevent one COVID-19 death at different times during this COVID-19 pandemic. We will consider the respective COVID-19 policies such as mask mandates, lock-downs, SARS-CoV-2 test mandates in our analyses and will evaluate the impact of these policies on COVID-19 deaths and diseases. In addition, we will evaluate data on total mortality according to the number of SARS-CoV-2 vaccinations and/or infections, and we will aim to collaborate with other research groups in order to extend our analyses.

In conclusion, the results of this study should provide an overview on the COVID-19 pandemic with respect to protection conferred by vaccinations and previous SARS-CoV-2 infections, as well as the health threat of SARS-CoV-2, in order to provide knowledge for future COVID-19 policy and future pandemics.