1 INTRODUCTION
On December 12, 2019, 27 pneumonia cases of unknown cause emerged in
Wuhan, Hubei, China.1 The etiological agent was
identified as a novel coronavirus and later renamed as severe acute
respiratory syndrome coronavirus 2 (SARS-CoV-2) by the International
Committee on Taxonomy of Viruses (ICTV).2-4 Community
transmission is now evident, and it is clear that SARS-CoV-2 is a highly
contagious virus.5 Until 9 May 2020, the coronavirus
disease 2019 (COVID-19) has wreaked havoc in 210 countries and
territories, affected more than 3.8 million cases and 265,862 deaths
around the world.6 SARS-CoV-2 infection induces
pneumonia, acute respiratory distress syndrome and death, particularly
in vulnerable populations such as elderly adults and those with chronic
medical conditions, such as cardiovascular diseases, diabetes,
respiratory diseases, hypertension and malignancy.7Knowledge on SARS-CoV-2 infection in children is still yet to be fully
developed and only limited studies on pediatric patients are currently
available.8-12
According to the Chinese expert consensus on the diagnosis, treatment
and prevention of SARS-CoV-2 infection in children (2nd Version),
pediatric COVID-19 cases are classified to five clinical types with
different severities: 1) asymptomatic infection; 2) acute upper
respiratory infection (AURI); 3) mild pneumonia; 4) severe pneumonia; 5)
critical pneumonia.13 In contrast to infected adults,
most infected children appear to have a milder clinical
course.8 Asymptomatic infections are not uncommon.
Despite that the clinical features of COVID-19 pediatric patients have
been established so far, the difference between children with pneumonia
and without pneumonia (asymptomatic and AURI), in aspects of clinical
features, laboratory findings, immunological changes and outcomes, were
not reported. In addition, the allergy status, and the information of
the allergic diseases-related laboratory findings of these patients,
have not been reported yet. Allergic diseases are common and with
increasing prevalence in children.14-16 Previous
studies showed virus infection is one of the triggers for the
exacerbation of asthma.17 However, there was limited
information about the association between asthma and coronaviruses
infection, especially SARS-CoV and Middle East respiratory syndrome
coronavirus (MERS-CoV).18,19 Most animal models
established for the research of SARS-CoV and MERS-CoV are also found
less relevant to asthma.20 On the other hand, atopic
sensitization had no effect on the severity of viral pneumonia in
children, as shown in a multi-center prospective study, but the history
of allergic diseases such as atopic dermatitis, food allergy and drug
allergy were associated with severe pneumonia.21 In a
previous study on 140 adult COVID-19 cases, allergic diseases and asthma
showed much less prevalence compared to population levels, suggesting
that allergy is not a predisposing factor for SARS-CoV-2
infection.22
This study aims to investigate the clinical and laboratory
characteristics of hospitalized COVID-19 pediatric patients, and to
reveal the relationship between SARS-CoV-2 infection, immune response
and allergic status, with a special focus on disease severity and
allergy in patients.