ABSTRACT
Many vaccine strategies have been developed to control the COVID-19 pandemic. This article presents the mechanisms of action and the efficacy of different vaccines including mRNA- and adenovirus-based vaccines. We will discuss the different vaccine targets, immune responses and allergic reactions which have been reported during the vaccination campaigns. Finally, the latest recommendations for the prevention and management of severe allergic reactions will be summarized. Copyright © 2021 Editions Medecine et Hygiene. All rights reserved.
ABSTRACT
Background: The role of T cell immunity in protection against COVID-19 in immunosuppressed patients who failed to mount serological responses remains ill defined. Hypothesis: Vaccine-based intradermal skin test (IDT) serves as a surrogate marker of T cell responses in seronegative immunosuppressed patients. Methods: We compared anti-SARS-CoV-2 antibodies and cellular responses in vaccinated immunosuppressed (IS) patients (n = 58), healthy unvaccinated naive controls (NC, n = 8) and healthy vaccinated controls (VC, n = 32) by Luminex, IFN-γ ELIPSOT and IDT 3 to 6 months after vaccination. In 3 VC we performed a skin biopsy 24h after IDT and performed single-cell RNAseq of the skin-infiltrating CD45+ cells Results: Seronegative NC had no detectable T cell responses and negative IDR, whereas VC had anti-SARS-CoV-2 antibodies (100%), positive ELIPSOT (90%) and IDR (90%). Overall IS patients had significantly less antibodies up to 39 weeks after vaccination compared to VC but similar ELIPSOT responses. ELISPOT was positive in 33.3 % and 66.6 % and IDR in 62.5% and 90.5% of seronegative vs seropositive IS patients respectively. Conversely, patients with negative IDR had significantly lower T cell responses and IgG titers than those with positive IDR. Importantly, the TCR repertoire of infiltrating skin lymphocytes revealed 18/1064 clonotypes with known specificities against SARS-CoV-2. Conclusion: Our results indicate that local reaction to IDR is partially composed of SARS-CoV-2-specific T cells. IDR represents a promising tool to cost-effectively monitor SARS-CoV-2 specific T cell immunity in IS patients.