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Patients on hemodialysis have been historically demonstrated to have poor seroconversion rates in response to vaccines. The aim of this study was to determine the adaptive humoral immune response by quantification of the neutralising antibody titre after covid vaccination.
The study was conducted at a tertiary care government multi super-specialty hospital in the southern part of India. Study participants were patients on maintenance haemodialysis and the study intervention involved two doses of Covishield (Astra Zeneca) vaccine administered 12 weeks apart. After informed consent, sampling for anti- SARS-CoV-2 S (spike) antibody was done by ECLIA (electrochemiluminescence) at baseline, 12 weeks after 1st vaccine dose, 4 weeks and 1 year after 2nd dose. Based on the antibody titre (expressed in U/mL), patients were categorised as non-responders (<0.4), poor (0.4-20), intermediate (20-250) and high responders (>250) after the 1st dose and as intermediate (<250) and high responders (>250) after the 2nd dose. Statistical analysis was done to determine association of the immune response with the following variables - age, gender, BMI, Charleson comorbidity score, prior SARS-CoV2 infection, time interval between prior covid infection and vaccination, hemoglobin level, white blood cell count, serum albumin and dialysis duration.
Baseline seropositivity was seen in 22.89% (n=19) of the 83 patients tested. Before 1st dose of vaccine, 9.8% (n=5) had previous SARS-CoV2 infection and the time interval between covid infection and 1st dose vaccine was 6.15 ± 0.49 months. The median baseline antibody level was 3.25 (0.4,35.74)U/mL and it was significantly higher in those with prior covid infection compared to others (p=0.013).
Of the 56 patients who received 1st dose of vaccine, 8.93% (n=5) developed SARS-CoV2 infection later. Median time interval between 1st dose vaccine and the covid infection was 14 (4.5, 31) days with 80% requiring hospitalization (n=4) and a mean hospital stay of 8.25 ± 3.97 days. All-cause mortality after 1st vaccine dose was 7.14% (n=4), of which 1 person died due to covid infection. Average time interval between 1st dose and death was 6 weeks. Early humoral response was observed in 94.12% (n=48) at 12 weeks after 1st dose. High antibody titre was observed in 68.6% (n=35) and was associated with higher baseline covid antibody level (p=0.001).
The humoral immune response after 2 doses of Covishield vaccine offered 100% protection from symptomatic covid infection at the end of 1 year in patients on hemodialysis.