SARS-CoV-2 antibody and T cell responses one year after COVID-19 and the booster effect of vaccination: A prospective cohort study

Abstract

Objectives : First, to describe SARS-CoV-2 T cell and antibody responses in a prospective cohort of healthcare workers that suffered from mild to moderate COVID-19 approximately one year ago. Second, to assess COVID-19 vaccine-induced immune responses in these prior-infected individuals. Methods : SARS-CoV-2-specific T cell and anti-SARS-CoV-2-Spike-RBD immunoglobulin G (IgG) responses in blood were determined before COVID-19 vaccination with mRNA-1273, BNT162b2, Ad26.CoV2-S or ChAdOx1-S, two weeks after first vaccination, and after second vaccination. Results : 55 prior SARS-CoV-2 infected and seroconverted individuals were included. S1-specific T cell responses and anti-RBD IgG were detectable one year post SARS-CoV-2 infection: 24 spot-forming cells per 10 6 peripheral blood mononuclear cells (SFCs/10 6 PBMCs) after S1 stimulation and anti-RBD IgG concentration of 74 (IQR 36-158) IU/mL. Responses after the first and second vaccination were comparable with S1-specfic T cell responses of 198 (IQR 137-359) and 180 (IQR 103-347) SFCs/10 6 PBMCs, and IgG concentrations of 6792 (IQR 3386-15180) and 6326 (IQR 2336-13440) IU/mL, respectively. These responses retained up to four months after vaccination. Conclusions : Both T cell and IgG responses against SARS-CoV-2 persist for up to one year after COVID-19. A second COVID-19 vaccination in prior-infected individuals did not further increase immune responses in comparison to one vaccination.

Differences in Humoral and Cellular Vaccine Responses to SARS-CoV-2 in Kidney and Liver Transplant Recipients

“…We found a relationship between anti-SARS-CoV-2 antibody formation and T cell responses, as documented by the fact that patients with antibody seroconversion (responders) had also higher levels of IFN-γ producing T cells at T2 ( Figure 4C ). These data confirm and expand previous findings by others ( 34 , 35 ). However, we also noticed patients with serological conversion that did not have detectable anti-SARS-CoV-2 IFN-γ T cell responses.…”

Complete (Humoral and Cellular) Response to Vaccination against COVID-19 in a Group of Healthcare Workers-Assessment of Factors Affecting Immunogenicity

“…Ferrari et al and Manisty et al investigated differences in the post-vaccination response in people who had previously had COVID and suggested using different vaccination schedules in individuals with past infection [ 21 , 22 ]. Krammer et al and Mak et al additionally showed that in persons with past SARS-CoV-2 infection (even more than a year before vaccination), the administration of one vaccine dose produces the same humoral and cellular response as administration of two vaccine doses [ 4 , 24 ].…”

“…A positive correlation of the symptom severity of SARS-CoV-2 infection with the antibody titre was also demonstrated by Wolszczak-Biedrzycka [ 14 ]. Although past infection is associated with preserving immunological memory even one year after infection [ 4 ], it can be expected to be weaker in certain groups. This includes the elderly, residents and staff of care homes, persons after paucisymptomatic infection and those with higher exposure [ 25 ].…”

“…However, especially in the graphical representation, it can be seen that there are those with a high cellular and low humoral response among the vaccinated individuals and the opposite with a high humoral and low cellular response. For the time being, it is difficult to explain these discrepancies, which researchers still study [ 4 , 37 ].…”

“…According to some researchers, if the virus slips through humoral protection, then the T-cell activity is the guarantee of a mild course of the disease [ 3 ]. However, in the light of current knowledge, it is difficult to determine the influence of cellular and humoral responses in protection against infection [ 2 , 4 ].…”