To the editor:
There has been a rapid response to vaccine development worldwide since the announcement of the COVID-19 pandemic in March 2020. Data is beginning to emerge demonstrating the safety, tolerability, immunogenicity and efficacy of COVID-19 vaccines in children and adolescents. 1, 2 While children and adolescents infected with SARS-CoV-2 suffer from milder disease than adults, those with underlying health co-morbidities, including cancer, may suffer from severe disease.3, 4 Minimizing exposure remains important in reducing the risk of SARS-CoV-2 infection in children with cancer5, but vaccination is emerging as a critical strategy for preventing infection, decreasing disease severity and contributing to immunity the herd.
Currently, there is a widespread recommendation for cancer patients to receive COVID-19 vaccination,6 supported by a prospective observational study in adults with cancer that identified safety and immunogenicity after vaccination with BNT162b2.7 Although inferior to healthy controls, seroconversion rates were better after an early second vaccine boost on day 21 and for patients with solid tumors compared to those with hematologic cancers. The latter is supported by a recent study, which found a blunted and heterogeneous antibody response to BNT162b2 vaccination in adults with haematological malignancies.8
There is a lack of data on COVID-19 vaccination in children with cancer; however, these findings have been reflected in studies of inactivated influenza and pneumococcal vaccination, which show that children with cancer can mount a protective immune response to vaccination, and that the degree of response is modulated by a variety of factors, including the number of doses received, regardless of whether treatment is given for a solid or haematological malignancy and lymphocyte counts at the time of vaccination.9-11 Since response patterns are reflective of host immunity, similar results are likely to be found following COVID-19 vaccination in children with cancer, suggesting that optimization of outcome can be achieved by timing immunization to the point furthest from the immunosuppressive effect of cytotoxic treatment during a given cycle. In addition, a specific consideration in vaccination of children with acute lymphoblastic leukemia is the presence of polyethylene glycol (PEG) as a stabilizing component of mRNA COVID-19 vaccines, requiring the development and validation of strategies to reduce the risk to children with a history . of hypersensitivity to PEG-asparaginase
The COVID-19 and Cancer Taskforce found that there is little planning on an international scale for systematically collecting data from cancer patients receiving COVID-19 vaccines.13 As COVID-19 vaccines become licensed for use in children and adolescents, there is a need to develop clinical trials in children with cancer to provide the best evidence. However, as access to trials will not be universal and the duration required to conduct a trial, it will be essential for global data collection for children with cancer vaccinated outside of a clinical trial setting. This should include a minimal clinical dataset, with reporting of safety data, including adverse events such as myocarditis and pericarditis,14 and a history of COVID-19 infection before and after vaccination. This is best facilitated by platforms such as the Global COVID-19 Observatory and Resource Center for Childhood Cancer, which continues to be an invaluable resource on COVID-19 for healthcare professionals treating children with cancer.3