Individuals who have recovered from SARS-CoV-2 infection were shown to have higher antibody response to a single dose of mRNA vaccines while memory response was demonstrated in COVID-19 patients up to 8 months. The efficacy of vaccines to generate immunological memory post vaccination has not been studied.
To assess immunological memory in previously infected individuals after a single dose of vector based vaccine PATIENTS AND METHODS: Healthcare workers (n = 280) were enrolled after obtaining written informed consent and grouped under previously infected (RT-PCR positive) and no prior exposure group (RT-PCR negative). Blood was drawn at baseline and post vaccination (single dose of COVISHIELD) for enumerating neutralizing antibodies by Chemiluminiscence and memory T and B cells employing flow cytometry.
A higher antibody response (1124.73 ± 869.13 vs94.23 ± 140.06 AU/ml; p = 0.0001), CD4 memory T-cells; central memory CCR7+CD45RA- (p = 0.0001), effector memory CCR7-/CD45RA- (0.01), total CD8+T cells; (p = 0.004), CD8+naïve T cells CCR7+CD45RA+; (p = 0.01) and memory B cells CD20+CD27+; (p = 0.0001) was seen in previously infected individuals with a single dose of vaccine.
Single dose vaccination elicited higher neutralizing antibody response and protective immunity in individuals who were previously infected. Hence single dose strategy may be pursued to increase population coverage.

Copyright © 2021. Published by Elsevier Ltd.