CLINICAL PROFILE OF COVID-19 INFECTION AND IMMUNE RESPONSE AFTER 3AND6 MONTH VACCINATION AGAINST SARS-COV-2 IN ADULT PATIENTS WITH TRANSFUSION-DEPENDENT THALASSAEMIATHE EXPERIENCE OF A GREEK CENTER

ABSTRACT

Background: Patients with transfusion-dependent-thalassaemia (TDT) are considered as increased risk population for severe and/or morbid COVID-19 infection. Timely vaccination is the main preventive method for severe COVID-19. Aims: To provide an overview of the clinical profile and outcome of COVID-19 infection in patients with TDT as well as to study the immune response after 3 and 6 months after vaccination against COVID-19 in adult patients with transfusion-dependent thalassaemia. Methods: This analysis focused on the evaluation in TDT patients on the long-term immune response post vaccination and on the course of COVID-19 infection and its correlation with immunization status. Serum was collected at 4 pre-defined time points, namely, just before 1st dose (TP1), 7 weeks after the 1st dose (TP2), 3 months (TP3) and 6 months (TP4) after 2nd dose. Neutralizing antibodies (NAbs) against SARS-CoV-2 were measured using FDA-approved methods. According to manufacturer, the scale of NAbs titer is 0-100%, with ≥30% considered as positive and ≥50% as clinically relevant viral inhibition. Age-matched healthy volunteers (median age 46 years, range 24-64 years, 24 males / 53 females) who received mRNA vaccines served as the control group for NAbs evaluation. Results: 340 (170female/170male) TDT patients older than 18 years (mean 43.6±11.5 years) followed in a single unit were included in the analysis. 270 patients (79%) were vaccinated with 2 or 3 doses. Immune response to vaccination was evaluated in 90 patients (median age 46 years, range 19-63 years, 40 males / 50 females). NAbs were at the level of non-immunity in all the patients at baseline (TP1) (mean 16.57% ±11.85) and showed a significant increase after the second dose (TP2) mean 86.96%±12.95 (p<0.0001). At TP3 and TP4 Nabs showed a significant decrease but remained in protective levels for the majority of the patients (mean 88.75% ±9.7 and 74.64% ±17.2 respectively(p<0.0001). The kinetics of NAbs were similar to controls except for levels at TP4 (p=0.02) (Figure 1). Up to 10/FEB/2022, 43 TDT patients (median age 43.52 range 18.6-57.9 years) were diagnosed with COVID-19, with 1 of them being infected twice. Of them, 17 were unvaccinated, 18 had received 2 doses of vaccine, while 8 had received 3 doses of the vaccine. The incidence rate was 9.6% and 24.3% for vaccinated and unvaccinated patients, respectively. The severity of the COVID-19 for vaccinated and unvaccinated patients were as follows, respectively, ;Grade 1 (asymptomatic) 0 and 1, Grade 2 (mild symptoms, symptomatic therapy, no COVID19 specific therapy) 23 and 9, Grade 3 (mild symptoms, symptomatic therapy, with COVID19 specific therapy) 1 and 3, Grade 4 (moderate pneumonia, thrombophlebitis, Hospitalization) 2 and 3, Grade 5 (Hospitalization requiring ICU, death) 0 and 1. Thrombotic event was documented in 1 patient. All patients except one from unvaccinated group are alive. Summary/Conclusion: Immune response to vaccination may wean faster in TDT patients. in Unvaccinated TDT patients were more likely to be infected and to develop more serious COVID-19 infection compared to vaccinated patients. (Figure Presented).