Discussion
The role of asthma as a risk factor for COVID-19 in children is undetermined, and some authors highlight the need for more data7. From the results of our series, we found that 11.1% of SARS-CoV-2 infected children suffer from asthma. This is consistent with the global prevalence of asthma collected by the ISAAC study1 from Europe and Spain, which is around 10.3% in the pediatric population. Based on these observations, we could consider that asthma is not a risk factor for SARS-CoV-2 infection in children.
However, a higher percentage of asthma has been observed in children who required admission or PICU (17.6% and 21.4% respectively), compared to children with mild infection (6.7%), although the difference did not reached statistical significance. We do not know if an increase in the sample size could have yielded other results. These data should be taken with caution since they have been obtained evaluating question 6 of the ISAAC questionnaire that considers the diagnosis of asthma at any time in the child’s life. However, when we analysed anti-asthmatic therapy in the previous year, both the use of salbutamol and inhaled corticosteroids were associated with increased risk of hospitalization, up to 8 times higher for salbutamol (4 times in the PICU) and up to 2.9 for budesonide (12 times in the PICU). These data lead us to suggest that active asthma could be a risk factor for more severe disease, higher rates of hospitalization and of PICU admission due to COVID.
Our results are consistent with Floyd et al8 study with more than 1000 children in Philadelphia, in which the authors did not find asthma to be a risk factor for hospitalization. However, the use of anti-asthmatic drugs was more frequent in hospitalized patients. Floyd et al, extracted data from the medical records, an important limitation of their study, while in our case the asthma diagnosis was made using an internationally validated questionnaire and was obtained directly from the parents, thereby reducing the bias of lack of data in the medical records.
Our findings are also similar to a systematic review carried out by Sunjaya et al9 in Australia, including 57 studies (only 4 included children) with more than 300,000 confirmed SARS-CoV-2 infections. The prevalence of asthma in SARS-CoV-2 patients was similar to the prevalence of global asthma (7.46%). Although the authors found a higher percentage of asthmatics with severe COVID-19 and higher requirement for ICU admission, the difference was not statistically significant.
Recently, a cross-sectional study of 43 465 patients under 18 years of age with COVID-19, has been published. More than 25% of patients had one or more underlying condition. Asthma was found to be a risk factor for hospitalization and clinical severity, although it is not specified whether asthma was a current or previous condition 10. Finally, Zu et al11, with a different approach, performed a study analysing the genetic predisposition to allergic asthma, employing data from the UK Biobank in 492,768 adult patients and they found an association between non-allergic asthma and severe COVID-19.
Despite our limitations, we conclude that a history of asthma was not a risk factor for SARS-CoV-2 infection in our series, but active asthma could be a risk factor for more severe evolution and need for hospitalization for COVID-19 in children. More studies are needed to clarify the role of asthma in pediatric population with COVID-19.
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