Abstract
Background: To determine the kinetics and persistence of immune responses following the Sinopharm/BBIBP-CorV, we investigated immune responses in a cohort of Sri Lankan individuals.
Methods: SARS-CoV-2 specific total antibodies were measured in 20-39 years (n = 61), 40-59 years (n = 120) and those >60 years of age (n = 22) by enzyme-linked immunosorbent assay, 12 weeks after the second dose of the vaccine. Angiotensin-converting enzyme 2 (ACE2) receptor blocking antibodies (ACE2R-Ab), antibodies to the receptor-binding domain (RBD) of the ancestral virus (WT) and variants of concern, were measured in a sub cohort. T cell responses and memory B cell responses were assessed by ELISpot assays.
Results: A total of 193/203 (95.07%) of individuals had detectable SARS-CoV-2 specific total antibodies, while 67/110 (60.9%) had ACE2R-Ab. A total of 14.3%-16.7% individuals in the 20-39 age groups had detectable antibodies to the RBD of the WT and variants of concern, while the positivity rates of those ≥60 years of age was <10%. A total of 14/49 (28.6%) had Interferon gamma ELISpot responses to overlapping peptides of the spike protein, while memory B cell responses were detected in 9/20 to the S1 recombinant protein. The total antibody levels and ACE2R-Ab declined from 2 to 12 weeks from the second dose, while ex vivo T cell responses remained unchanged. The decline in ACE2R-Ab levels was significant among the 40-59 (p = .0007) and ≥60 (p = .005) age groups.
Conclusions: Antibody responses declined in all age groups, especially in those ≥60 years, while T cell responses persisted. The effect of waning of immunity on hospitalization and severe disease should be assessed by long term efficacy studies.
Keywords: COVID-19; Sinopharm/BBIBP-CorV; antibody; kinetics; persistence; vaccines.
【저자키워드】 COVID-19, Vaccines, antibody, Kinetics, persistence, Sinopharm/BBIBP-CorV, 【초록키워드】 SARS-CoV-2, Efficacy, ACE2, immune response, Immunity, Hospitalization, Vaccines, Antibody Response, variants of concern, peptide, virus, variants, Spike protein, Protein, enzyme-linked immunosorbent assay, Kinetics, Cohort, T cell, Antibody responses, Receptor-binding domain, RBD, immune responses, response, T cell responses, peptides, age, ELISPOT, receptor, total antibody, group, T cell response, memory B cell, Sinopharm, Angiotensin-converting enzyme, interferon gamma, angiotensin, severe disease, long term, Ex vivo, overlapping, blocking antibodies, second dose, enzyme, individual, all age groups, total antibodies, ELISpot assays, Cell, enzyme-linked immunosorbent, memory B, assays, investigated, remained, detectable, determine, the spike protein, the RBD, the receptor-binding domain, individuals, groups, the vaccine, were measured, declined, were assessed, 【제목키워드】 Vaccine, immune response,