| Abstract |
Background: The rapid spread of Covid-19 infection worldwide triggered emergency mechanisms to contain the pandemic, with the manufacture and eventual administration of vaccines against the SARS-CoV-2 virus. Final immunization with a combination of vaccines is 93-96% effective, reducing pathogenesis, hospitalization and mortality. A challenge was the mutagenesis of the virus that affected the effectiveness of the vaccination as well as the longer time distance since the last booster dose, as a result of which new waves of pandemic appeared periodically worldwide.
Objective: The purpose of this thesis is to study the effect of vaccination against the SARS-CoV-2 virus on the severity of the disease and the outcome of patients with COVID-19 infection who were hospitalized at the University General Hospital of Heraklion during the pandemic.
Methods: In this retrospective study, the patients that included in the sample were PCR positive and were hospitalized for >48hr at the MAK PAGNI clinic between 18/3/20 and 10/10/22. They were grouped by vaccination status according to ECDC criteria and examined and compared during the pre-Delta, Delta and Omicron periods. The parameters studied were demographic data, comorbidities, disease severity, therapeutic agents received, clinical-laboratory findings, complications, and hospitalization outcome.
Results: From 1940 patients, 381 were excluded, and 1559 patients were included in the study, of which 663 (42.5%) were vaccinated. Patient characteristics were median age 70 years (IQR 56;81), male 890 (57.1%), co-morbidity 1354 (86.9%), ICU admission 147 (9.4%), median length of stay in MAK 7 days (IQR). 5;11), mortality 184 (11.8%). In the pro-Delta period 476 (30.5%) patients were identified, in Delta 356 (22.8%) and in Omicron 727 (46.6%). Vaccinated patients were 663 (42.5%), of whom 30/663 (4.5%) were partially vaccinated, 275/663 (41.4%) were fully vaccinated, 320 (48.2 %) 3rd booster dose and 38 (5.9%) had received 4th booster dose. The number of vaccinated patients differed between time periods (pro-Delta 37 (5.6%) vs Delta 121 (18.3%) vs Omicron 505 (76.2%), p<0.001). Predominant symptoms on admission to the ICU were hypoxemia (p=0.003) and dyspnea (p<0.001) and were related to the absence of vaccination. No specific co-morbidity was associated with exacerbation and ICU admission, except mental illness (p=0.011) and dementia (p=0.005). A higher number of co-morbidities was associated with mortality (p<0.001). Pulmonary embolism occurred in 64 (4.1%) patients and was not associated with vaccination, ICU admission, or mortality. A total of 244 (15.7%) patients were placed in the prone position, which was statistically significantly associated with vaccination (EMB 6% vs Mη-EMB 22.9%, p<0.001), ICU admission and mortality (p<0.001). Hyperimmune plasma was received by 97 (6.2%) patients and monoclonal antibodies by 132 (8.5%), which were positively associated with ICU admission (p<0.001) and mortality (p<0.011). MAK patients who developed severe disease and were admitted to the ICU were predominantly male (p<0.001), more often in the pro-Delta (11.97%) and Delta (11.52%) period versus Omicron (6.74%) (p=0.003 ), and had low oxygenation indices (PF ratio and ROX index) on the day of admission and on the day of exacerbation (all p<0.001). Vaccination coverage was shown to be protective for ICU admission in all mutation periods (p<0.001). Vaccination protected patients from severe disease in the Delta (p=0.005) and Omicron (p=0.002) periods, but not for pre-Delta (p=0.186). After logistic regression analysis, embolization was an independent association factor with ICU admission (p<0.001), while the more doses of vaccine the patient had received, the lower the risk of ICU admission (p<0.001). Patients who ultimately died were older (p<0.001), had multiple comorbidities (p<0.001), had some type of malignancy (p<0.001) and had severe respiratory failure on the day of admission to the ICU (p<0.001) (logistic regression analysis). Having a 4th vaccination dose was an independent protective factor associated with mortality (exp(B) 0.725, p=0.043). ROC analysis showed that low PF ratio and ROX index on admission and day of deterioration proved to be better predictors of ICU admission, while non-vaccination, old age, comorbidities, presence of malignancy and low PF ratio proved to be better predictors of mortality.
Conclusion: Risk factors for morbidity and mortality following a COVID-19 infection are old age combined with male gender male, comorbidities and respiratory failure. Vaccinated patients, including the booster dose, were less likely to be admitted to the ICU and die compared to non-vaccinated patients.
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