DURABILITY OF HUMORAL AND CELL-MEDIATED IMMUNE RESPONSE AFTER SARS-CoV-2 mRNA VACCINE ADMINISTRATION.

Vaccination against the SARS-Cov-2 virus is an effective way to protect against the disease and the severe course of COVID-19. Forty-nine fully vaccinated with mRNA vaccines (BNT162b2 or mRNA-1273) SARS-CoV-2 infection-naïve volunteers aged 33-89 were enrolled in the study. Evaluation of the cellular and humoral immune response was performed within 1 to 3 months (T1) and 6-9 months (T2) after the second injection, and within 2-3 months (T3) after a booster dose. Additionally, a comparative analysis of the specific immune status was made between two age groups - below 60 (n=22) and over 60 (n=27) years. SARS-CoV-2-specific T-cell response was evaluated by IFN-γ-producing spot forming cells (SFCs) using a standardized ELISPOT assay. Virus neutralizing antibodies (VNA) against SARS-CoV-2 were measured by a blocking ELISA test and spike protein specific IgG (S-IgG) and IgA (S-IgA) antibodies - by semi-quantitative ELISA. IFN-γ-producing SFCs, S-IgG, S-IgA and VNA significantly decreased 6-9 months after the second dose. After the third injection S-IgG and S-IgA markedly increased compared to T2 and reached the levels at T1. Of note, the highest values of VNA were observed at T3. No differences in the tested immune parameters were found between the two age groups. Data obtained showed that for a long period - 6-9 months after a full course of immunization with mRNA vaccine, immune reactivity is present, but both cellular and humoral immune responses gradually decrease. The administration of a third dose mainly restores the specific humoral immune response against the SARS-CoV-2 virus. This article is protected by copyright. All rights reserved.

Students' Attitudes toward COVID-19 Vaccination: An Inter-University Study from Bulgaria.

In Bulgaria, vaccination coverage against the SARS-CoV-2 virus is low. The reasons for this fact are many and varied. The aim of the present study was to establish what the attitudes towards the COVID-19 vaccination process are among students from various specialties from several Bulgarian universities. In this research, 600 students participated, divided into two groups: Doctor of Medicine (MD) students (n = 300) and non-MD students, i.e., students of specialties, such as mathematics, engineering, finance and economics, law, human sciences, etc. (n = 300). Each respondent completed a questionnaire which was divided into three parts with closed questions. The mean age of all students was 21.19 ± 1.87 years (95% CI: 20.48-21.90). The female sex dominated among the analyzed participants (sex ratio: female/male = 1/0.85). Nearly 62% (371/600) of individuals declared that they have been COVID-19 vaccinated with at least one dose (p < 0.001). Overall, 33% of the participants sought information on vaccines from video sharing platforms and 36.0% (216/600) from social media platforms. From the conducted multivariable logistic regression the odds of vaccination against COVID-19 were 6.225 times higher in individuals with a positive attitude towards these vaccines than in people with a negative attitude towards them (p < 0.001). We have found that those students who trust the international health organizations had an OR of 2.365 (p = 0.004) to be SARS-CoV-2 vaccinated. We estimated that the odds of vaccination against SARS-CoV-2 among children were 4.794 times higher in parents (students) who had been vaccinated than in non-vaccinated parents (students) (p < 0.001). Our results could support the national public health organizations, the national educational/scientific systems, and the management of Bulgarian universities in making future decisions about the field of COVID-19 control and prevention.

Hydroxychloroquine (HCQ) Treatment for Hospitalized Patients with COVID- 19.

OBJECTIVE: Studies have indicated that hydroxychloroquine (HCQ) exerts antiviral effects against SARS-CoV-2 in vitro. However, trials regarding its effects on patients are very controversial. This study aims to evaluate the efficacy of (HCQ) in the treatment of hospitalized patients with COVID-19. METHODS: We prospectively enrolled 260 patients hospitalized for COVID-19 in Heart and Brain Center of Excellence- Pleven, Bulgaria, for the period from November 6 to December 28, 2020. This study is not randomized, which we compensated for with Propensity Score Matching. Patients in the HCQ group were given HCQ 200 mg 3 times a day (600mg daily) for the duration of their hospitalization plus conventional treatment, while those in the control group were given conventional treatment only. The primary endpoints were transferred to the intensive care unit, needed for mechanical ventilation, and in-hospital death. RESULTS: Of the 260 COVID-19 patients, 178 (68.5%) were male and the mean age was of 63.78 ± 12.45 years, with the most prevalent comorbidity hypertension (68.5%). We had two subgroups: treated with HCQ and conventional treatment (128 patients) and treated with conventional treatment only (132 patients). In the primary analysis, patients in the HCQ group presented with fewer comorbidities and were younger than the group without HCQ. Patients treated with HCQ demonstrated a significant benefit in the primary endpoints compared to those without HCQ, namely, transferred to ICU - 20 (20,8%) vs. 41 (36.9%), p=0.011, need for mechanical ventilation 13 (13.4%) vs. 33 (28.2%), p=0.009 and in-hospital death 14 (10.9%) vs. 35 (26.5%), p=0,001, respectively. We repeated this analysis with PSM, where 70 matched pairs were identified. Regarding the primary endpoints, we found again a statistically significant difference between the groups. Comparing transferring to ICU, better outcomes were presented in the HCQ group: 8 (17.4%) vs. 27 (44.3%), with p= 0.003. Besides, a smaller proportion of the patients needed mechanical ventilation: 6 (12.8%), compared to the control group, 23 (35.4%), p= 0.007. Notably, patients from the HCQ group died during hospitalization: 8 (11.4%) in comparison with 19 (27.1%) from the control group, p= 0.018. CONCLUSION: Patients treated with HCQ demonstrated a significant benefit in the primary endpoints in our study, namely, transfer to the intensive care unit, need for mechanical ventilation, and in-hospital death. HCQ improves prognosis in hospitalized patients with COVID-19.

Clinical Characteristics of Hospitalized Patients with COVID-19 in Sofia, Bulgaria.

Introduction: SARS-CoV-2 infection is spreading around the world, including countries from Southeastern Europe. The purpose of the study was to present the clinical manifestations of COVID-19 patients admitted to the Military Medical Academy, Sofia, Bulgaria. Materials and Methods: A retrospective study was conducted for a period of 3 months from March 2020 to June 2020 on this infection in our hospital. All participants were laboratory confirmed cases of COVID-19. RT-PCR was performed for etiological diagnosis. The hospitalized patients were divided into two groups on admission, that is, nonsevere and severe. Results: One hundred thirty-eight COVID-19 patients were hospitalized and analyzed during the study period. The mean age was 52.9 years. Male was the dominant sex (sex ratio: male/female = 1/0.6). The leading clinical signs were fever, fatigue, cough, and headache. On comparative analysis of both groups (nonsevere and severe) was measured significant elevation of white blood cells (odds ratio [OR] = 1.238; p value = 0.006), C-reactive protein (OR = 1.021; p < 0.001), creatinine (OR = 1.037; p < 0.001), aspartate aminotransferase (OR = 1.014; p = 0.040), lactate dehydrogenase (OR = 1.004; p < 0.001), ferritin (OR = 1.002; p < 0.001), fibrinogen (OR = 2.028; p < 0.001), and d-dimer (OR = 2.162; p = 0.002) in severe group than in nonsevere group. Interleukin 6 was tested in 17.4% of patients and high value was found-38.6 pg/mL (95% confidence interval: 16.5-60.7). Conclusion: The first Bulgarian retrospective study of COVID-19 hospitalized patients was presented. Older age, male sex, comorbidity, and signs of dyspnea and nausea were estimated as higher risk factors for severe form. Abnormality in inflammatory markers was associated with poor progression of the illness.