RESULTS
After removing duplicates, the first search yielded eight systematic
reviews(5, 8-14). Three of them were eliminated
because they did include information on clinical characteristics in
children(8-10). Therefore, we evaluated five
systematic reviews done at different periods during the pandemic and
thus including somewhat different primary
studies(11-14). Castagnoli et
al.(11) included 18 articles, 17 from China and 1 from
Singapore (444 patients <10 years old and 553 aged 10-19
years), published up to March 3, 2020. Choi et al.(12)included 7 articles from China (225 pediatric patients) up to March 12,
2020. Chang et al.(13) included 9 studies from China
(93 pediatric patients) up to March 15, 2020. The review by
Ludvigsson(14) included 45 studies from China (the
total number of patients was not described) up to March 19, 2020. And
Streng et al.(15) included 8 studies from China
(ranging from 6 to 2,143 patients) and one survey from Germany (33
patients) in hospitalized children, up to March 31, 2020. After
excluding duplicates, we identified and reviewed 67 primary studies
included in those five reviews (see Supplementary Table
1 ).
None of the primary studies reviewed reported asthma or recurrent
wheezing as a comorbidity or risk factor for COVID-19. Instead, some of
those studies reported young age (especially children <1 year
of age) as a group with more severe COVID-19. One large Chinese
study(16) reported non-respiratory chronic conditions
(hydronephrosis, leukemia receiving chemotherapy, and intussusception)
among the 3 children required ICU support and mechanical ventilation all
had coexisting conditions; one death occurred in the 10-month child with
intussusception. Another study reported a patient develop shock with
metabolic acidosis requiring ICU(17); while a report
from China(18) described one patient aged 10-19 years
who died, without other clinical information, that probably is the same
death in a 14-year-old boy described by Dong and
colleagues(19). Unfortunately, the two larger studies
in Chinese pediatric patients, Dong et al.(19) (2,413
children) and Wu and MacGoogan(20) (965 children) did
not report enough clinical data to identify comorbidities or risk
factors for COVID-19 severity. In the German survey of 33 hospitalized
children, 4 out of 22 (18%) children with clinical information had
“respiratory comorbidities” without further
details(15).
Our second search yielded 34 results in PubMed. Of those, five were
primary studies that reported on asthma in
adults(21-25); one other was a guidance
statement(26) that referenced a primary report that
also included information on asthma in adults(27). No
studies from that search included information on asthma in children,
although one case series reported two young children (ages 2 and 3
years) with history of atopic dermatitis and allergic rhinitis, who were
hospitalized with COVID-19; both patients
recovered(28).
Our third search yielded 26 pre-prints in BioRxiv and 137 in MedRxiv.
None of the BioRxiv posts were relevant to our topic. Of the 137
pre-prints in MedRxiv, 23 non-duplicate studies included information on
asthma(29-51), but none of them included specific
information in children.
More recently, the CDC published a Morbidity Mortality Weekly Report
(MMWR)(52) that included information from 2,572 U.S.
children aged < 18 years. Of those cases, 345 had data on
clinical and underlying conditions, and 80 of those children (23%) had
at least one underlying condition. The most common underlying conditions
were “chronic lung diseases (including asthma)” in 40 children,
cardiovascular disease in 25, and immunosuppression in 10; separate
information on asthma was not provided. Among the 295 cases for which
data on both hospitalization status and underlying medical conditions
was available, 28/37 (77%) hospitalized patients had one or more
underlying medical condition (including all six patients admitted to an
ICU); compared to 30/258 (12%) patients who were not
hospitalized(52). Finally, a recently published
Italian study, including100 children seen in 17 emergency departments,
reported that 27% had comorbidities without more specifications, and no
deaths occurred(53).