Vaccine breakthrough cases among hospitalised patients in the intensive care unit for covid-19 in north-eastern bulgaria

Background: COVID-19, caused by SARS-CoV-2, continues to spread globally, with vaccines being the most effective way to control the pandemic. Studies show a significant reduction in infection, hospitalisations, severe disease, and death after vaccination. The aim of the study was to determine the share of breakthrough infections among critically ill patients with severe COVID-19 who had been admitted to the intensive care unit (ICU) of a hospital at the beginning of the delta-variant pick. Material and methods: For a period of 10 months a total of 740 patients diagnosed with COVID-19, were treated in the intensive care unit of the University Hospital “St. Marina-Varna”, with ersons. Information on the vaccination status of all 740 hospitalised patients was extracted from the National information system "Register of immunized persons against COVID-19", including the type and date of COVID-19 vaccine administration, where available. After that, descriptive statistics were performed with the collected data. Results: Out of 740 patients, 19 (2.6%) had received at least 1 dose of vaccine, and 721 (97.4%) - none. Only ten (1.35%) of the studied everely and critically ill patients had completed the vaccination cycle (without a booster dose). Conclusion: Our findings show that when fully administered, vaccines are highly effective against laboratory-confirmed SARS-CoV-2 infection leading to ICU admission. Our findings reinforce the value of widespread COVID-19 vaccination, underscore the importance of completing the vaccination cycle for either of the mRNA-based vaccines, and may help motivate persons who remain hesitant about being vaccinated.