1 Introduction
Environmental exposures such as maternal smoking, socio-economic status,
family structures, mode of delivery, diet, air pollutants and allergens
are well-known risk factors for childhood asthma.1,2 A
strong risk factor for increased asthma incidence and severity are also
frequent lower respiratory tract infections and multiple-trigger
wheezing during early life, which are significant predictors for the
subsequent development of asthma later in life.3,4
The relationship between asthma and respiratory infections has made
asthma an empirical risk factor for severe COVID-19 disease since the
beginning of the pandemic. Although this relationship remains to date
inconclusive with some reports suggesting that childhood asthma may be
even protective against COVID-19,5 at least during the
first months of the pandemic, COVID-19 control strategies characterised
asthmatic adults and children as potentially vulnerable
subpopulations.6
COVID-19 control strategies focused on containment of the spread of
COVID-19 and involved national lockdowns, social distancing, compulsory
use of masks and, following the roll-out of SARS-Cov-2 vaccines,
campaigns and assessment of vaccination status upon entering indoor
micro-environments. Not surprisingly, these strategies, combined with
concerns of contracting the virus, have resulted in behavioural changes
in the population, that, in turn, may have affected the epidemiology of
common chronic diseases such as childhood asthma.7Decreased time spent outdoors, leading to reduced exposure to ambient
environmental triggers such as allergens, pollutants and dust-related
particulate matter,8 as well as reduction of social
interactions that led to decreased exposure to communicable pathogens
such as the influenza virus, respiratory syncytial virus (RSV) and
rhinoviruses (RV) are the most relevant behavioural alterations that may
have affected asthma morbidity.9 In addition, other
COVID-19 control strategies also included stricter hand hygiene, while
during peak periods of the pandemic waves access to hospital or primary
care practitioners was restricted or avoided. In the case of children
with asthma, national containment strategies also involved school
closures,10 as well as restriction of after school
(mostly outdoor) activities.8 Published evidence over
the last two years has consistently documented a marked reduction of
asthma morbidity during the COVID-19 period, mainly in terms of reduced
exacerbation-related hospital and emergency department (ED)
encounters.11-16
The aim of this review is to
summarize the behavioural changes observed in asthmatic children during
the implementation of COVID-19 containment strategies, present the
concurrent improvement of childhood asthma morbidity and discuss the
possible implications of these observations for public health and
clinical practice in the post-COVID-19 era.