2.1 Study participants
This was a retrospective study and conducted in Xinhua Hospital, a large
tertiary hospital in Shanghai, China. The inclusion criteria for the
study were: pneumonia patients admitted to
the Department of Pediatric
Pulmonology of Xinhua Hospital from March to August 2020 (during the
COVID-19 pandemic when all students studied online at home and
strengthened personal protection) and in the same period of 2019 (prior
to the COVID-19 pandemic when all students studied at school) ; negative
for COVID-19; and aged 3 months to 16 years. Children were diagnosed
with pneumonia or severe pneumonia based on the criteria recommended by
the 2011 pediatric community-acquired pneumonia
guidelines18. Since the COVID-19 pandemic, all
pneumonia patients were screened for COVID-19 using real-time reverse
transcriptase polymerase chain reaction and each recruited child was
confirmed negative for COVID-19. Patients with congenital abnormalities,
immunodeficiency, metabolic disorders, chronic conditions, underlying
lung diseases, airway foreign bodies, tuberculosis or nosocomial
respiratory infections were excluded from this study.
Written informed consent was obtained from parents or legal guardians
for all the subjects who are under 16. The study was approved by the
Ethics Committee of Xinhua Hospital (approval number: Approval No.
XHEC-D-2023-019), and conducted according to the principles in the
Declaration of Helsinki.