1. INTRODUCTION
The coronavirus disease 2019 (COVID-19) pandemic, caused by infection with the severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2), has led to alarming numbers of infections and deaths worldwide since it was firstly reported in December 20191. SARS-CoV-2 belongs to the beta-coronavirus genus and is closely related to SARS-CoV2. SARS-CoV-2 binds to angiotensin-converting enzyme 2 (ACE2) via its spike protein to enter cells3. The host serine protease transmembrane protease serine 2 (TMPRSS2) cleaves the spike protein and thus enable cellular membrane fusion4,5. The host protease furin cleaves the full-length spike precursor to S1 and S2 peptides6. S1 directly binds to neuropilin-1 on the cell surface and may facilitate cell invasion and infectivity of SARS-CoV-26,7. ACE2 and TMPRSS2 are expressed at the epithelial sites of the lung and skin, whereas other host molecules that may be involved in SARS-CoV-2 invasion such as CD147, cyclophilins, CD26 and related molecules are expressed in both epithelium and immune cells8. The global administration of COVID-19 vaccines has dramatically decreased the infection rate, severity and mortality of this disease9,10. However, new SARS-CoV-2 variants of concern (VOC) of have emerged that will dampen the protective immunity induced by natural infection and current vaccines and lead to breakthrough infection11,12.
In this review, we highlight recent studies on the clinical and immunological characteristics of COVID-19 in the context of allergy and asthma. The impact of asthma on the susceptibility and severity of COVID-19 is not fully understood and it is discussed here in further detail. Moreover, recent studies on the immune responses and protective effects of COVID-19 vaccines are summarized. The possible culprit components of the vaccines that can induce an allergic reaction are elaborated, along with appropriate vaccination measures for reducing the risk of anaphylaxis.
clinical AND LABoratory characteristics of COVID-19