Material and Methods:
Study design and population:
This was a prospective longitudinal cohort study involving 36 health
care workers (HCW) and 19 cirrhosis patients at King George’s Medical
University and Sanjay Gandhi Postgraduate Institute of Medical Sciences,
Lucknow. Blood samples of 10 healthy unvaccinated (and unexposed as per
history) individuals were obtained from rural area and they were
referred for vaccination at primary health care center. The normal
healthy HCW were defined as without any co-morbidity or medication.
Patients were selected for the cirrhotic group based on clinical,
biochemical and radiological finding along as well as evidence of portal
hypertension and AST-Platelet ratio index. Hepatic decompensation was
determined by the presence of ascites or hepatic encephalopathy in cases
of hepatitis B-related liver cirrhosis, or by a markedly raised serum
bilirubin level along with prolonged prothrombin time or international
normalized ratio >1.5. 20 Venous blood
was collected from all participants before receiving the first dose (day
0) and before booster dose (day 270±14 after second dose or ≅ one year
after first dose). The time interval between first and second dose was
three months as per government protocol at the time of vaccination.
Samples were collected in plain and EDTA vial for anti-SARS-CoV-2
antibody and flow cytometry assay respectively. All participant signed
written informed consent form and study was approved by institutional
ethical committee.
Serological assay:
Anti-receptor binding domain (RBD) or anti-Spike antibody titer and
neutralizing antibody (NAb) were measured in stored serum sample by
double-antigen sandwich enzyme-linked immunoassay (ELISA) through
Elecsys® Anti-SARS-CoV-2 S (Roche Diagnostics GmbH, Germany) and
SARS-CoV-2 Neutralizing Antibody competitive ELISA Kit (Invitrogen,
Thermo-Fischer) respectively. The Elecsys® Anti-SARS-CoV-2 S antibody
titer is expressed as U/mL and value >0.8 U/mL was
considered positive (quantitation limit of 0.40–250 U/mL). For
SARS-CoV-2 Neutralizing Antibody, samples with more than 20% calculated
neutralization were considered positive.