Variation in the rate of diagnosis of childhood acute lymphoblastic leukemia in about to the COVID-19 Pandemic: a single-center study

Background. Greaves delayed infection hypothesis states that acute lymphoblastic leukemia (ALL) in children develops in two critical steps, with the first step (first hit) occurring in utero and the second step (second hit) occurring in the postnatal period and involving leukemia-associated genetic changes, depending upon the timing of exposure to common childhood infections. In this study, we investigated whether isolation of children at home as part of the lockdown during the Coronavirus Disease 2019 (COVID-19) pandemic resulted in a reduction in the number of new childhood ALL cases by avoiding the second hit. Materials and metods. This retrospective study included all newly diagnosed pediatric ALL patients aged 1–18 years. The study periods were from 15 March 2020 to 31 December 2020 (COVID-19 lockdown period) and from 15 March 2019 to 31 December 2019 (control period). Results. Acute leukemia was diagnosed in 73 children between January 2019 and December 2020. Of these, there were 58 ALL cases and 15 acute myeloid leukemia cases. During the COVID-19 lockdown period, 14 of the children were diagnosed with ALL. In the control period, 21 children were diagnosed with ALL. No pediatric patients diagnosed with ALL in August, September, and October 2020. Conclusions. We observed a reduced incidence within the lockdown period, possibly related to the potential role of SARS-CoV-2 infection as a second hit in childhood ALL.