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