About a tenth of coronavirus disease 2019 (COVID-19) cases in the UK, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), occur in children. The number of infected children who eventually need hospitalization is small, but about one in five of them will have critical COVID-19. It is important to identify children with risk factors for severe disease, as vaccination could be extended to them on a priority basis.

Study: Risk of COVID-19 hospital admission among children aged 5–17 years with asthma in Scotland: a national incident cohort study. Image Credit: danielmarin/Shutterstock

Children with asthma formed the focus of the current study, which was carried out on behalf of the UK's Joint Commission on Vaccination and Immunisation (JCVI). The task included the identification of high-risk children with asthma.

Asthma was chosen because it is among the most common chronic illnesses in childhood. Despite the low absolute numbers of acutely ill children with COVID-19 and the uncertainty of vaccine-associated severe adverse effects, the need for vaccination of this group of children could be decided only based on the risk of hospitalization with COVID-19.

What did the study show?

The paper, published in the journal The Lancet Respiratory Medicine, describes a national cohort study including all children in Scotland between the ages of 5 and 17 years who were part of the Early Pandemic Evaluation and Enhanced Surveillance of COVID-19 (EAVE II). Children with uncontrolled asthma were identified by a history of previous hospitalization with asthma or treatment with an oral steroid over the two years before the study.

The investigators used a Cox proportional hazard model to find hazard ratios for hospitalization with COVID-19 among children with asthma, classifying them by asthma severity. The study included almost 63,500 children with asthma, of whom almost 7% (>4,300) were confirmed to have SARS-CoV-2 infection by the reverse transcriptase-polymerase chain reaction (RT-PCR) test. Among these, 67 were hospitalized, making up 1.5% of the total infected cohort.

When children with well-controlled asthma were compared to those with poorly-controlled or uncontrolled asthma, the rate of hospitalization with COVID-19 was higher in the latter subset. Children hospitalized with asthma over the previous two years were at more than six times higher risk of being hospitalized than non-asthmatic children. In contrast, those with well-controlled asthma were at 1.36 times the risk of non-asthmatic children.

If those who had previously been on oral steroids over the previous two years were considered to have uncontrolled asthma, the risk was greater than non-asthmatic children. Those with a history of three or more courses of the drug were at 3.4 times higher risk for hospitalization, vs. 3.5 with two earlier courses of treatment with oral steroids.

For those who had received only one course or none, the risk was 50% and 34% higher than those without asthma.

Interestingly, children between 5 and 11 years were also at higher risk for hospital admission with COVID-19 without either of these two markers of severe asthma. The higher level of testing may explain this among children with asthma due to a greater chance of seeking healthcare among the caregivers of such children, along with physician readiness to admit them.

Among children aged 5-11 years, those with asthma but no history of hospitalization were at twice the risk of COVID-19-associated hospitalization, compared to almost four times among those who had been hospitalized earlier with asthma. Among those aged 12-17 years, the risk was ten times greater.

If they had taken oral steroids earlier, the risk for hospitalization was three times after two courses, vs. almost five times higher after three or more courses. Correspondingly, the risk among 12-17-year-olds was 80% higher even after a single course of steroids before the COVID-19 episode but went up four times and two times, respectively, with two and three (or more) courses.

What are the implications?

The study shows that children of school age, between 5 and 17 years of age, are at over three times higher risk of being hospitalized with COVID-19 if they have taken two or more courses of oral steroids. With a prior history of hospitalization for asthma, the risk for COVID-19-associated hospitalization was six times higher.  In absolute numerical terms, this puts approximately 2,000 children across Scotland at risk, but approximately 110,000 children over the UK.

This is the first national-level population-based study on the risk of hospitalization following SARS-CoV-2 infection in this age group if uncontrolled asthma is present. The increased risk agrees with other studies showing that poor control of asthma increases the risk of hospitalization with COVID-19.

Building on this work, it is important for more detailed characterization of markers of asthma control for severe COVID-19 outcomes in children and to investigate underlying mechanisms that predispose such children to these increased risks.”

Asthma control is also key to minimizing the risks following SARS-CoV-2 infection.

This data will add to the evidence surrounding the spread of the virus among children, the course of the infection in this age group, and the need to achieve good asthma control and use other measures to contain viral transmission among children.