DISCUSSION
A common national registry of children with SARS-CoV-2 aims to assess more accurately whether cancer leads to more severe COVID-19. In our analysis, severe COVID-19 was more frequently detected in children without comorbidities (15%) than in children with cancer (7,1%), except in the case of recent alloHSCT (35.7%), as other studies reflected (8,12), but unrelated to the date of HSCT.
Despite a mild cancer course in children, the mortality rate is 1.6%, which, in our records, is associated with recent alloHSCT or other comorbidities. These rate is similar to the global GRCCC study (2), although with lower mortality (3.8%), probably because our patient’s data are located in a high-income country and during periods where less severe variants were included (13). Indeed, we found a milder infection, although not statistically significant, in the later phases of the pandemic and in vaccinated patients (14–16), and no deaths were recorded among them. Additionally, other comorbidities increased the severity in patients with cancer, although their impact was less than in patients without oncological diseases. Chemotherapy and radiation therapy did not seem to be related to clinical severity (17).
Nosocomial transmission was higher among children with cancer (11,2% vs 0,8%, p<0,001) , probably due to more frequent hospital visits. However, school transmission rates were similar between children with and without cancer, which may be useful to avoid changing the schooling plan of patients.
Study limitations of selection bias need to be acknowledged, since the initial screening policies in pediatric oncology units could result in a higher registration of mild cases. However, there were no reported cases requiring oxygen or admission to intensive care units in patients with ALL in maintenance, which highlights the mildness of COVID-19 in this population (18,19).
In conclusion, our data show that the infection is not more severe in patients with cancer/alloHSCT, except in patients with recent alloHSCT or additional comorbidities. These data support, in high-income countries, a policy of infection management similar to that with other respiratory viral infections in cancer pediatric patients, directed by the patient’s clinical status or other comorbidities rather than by isolation of SARS-CoV-2.