Effectiveness of Paxlovid in the treatment of the SARS-CoV-2 Omicron variant infection in children with hematologic malignancies: a retrospective cohort study

Background: Patients with hematologic malignancies (HMs) may be immunocompromised after receiving anti-tumor therapy. Those who also have the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus infection face many challenges, including a lack of effective antiviral drugs. This study aimed to investigate the clinical features of the SARS-CoV-2 Omicron variant infection in children with HMs, and the effectiveness of Paxlovid. Methods: A retrospective, non-randomized study was conducted on pediatric patients with HMs infected with the SARS-CoV-2 Omicron variant who had been admitted to the Shanghai Children's Medical Center, Shanghai, China from December 1, 2022 to March 1, 2023. The Paxlovid-treated group (Group P) comprised 21 patients, and the non-Paxlovid-treated group (Group N) comprised 21 patients. The patients' demographic data, clinical features, and therapeutic outcomes were collected. Statistical tests were used to evaluate the effectiveness of the treatment and related factors. Results: The clinical course of the SARS-CoV-2 Omicron variant infection for most of the children with HMs was non-severe (97.6%), and only one child progressed to severe disease (2.4%). The most common symptoms were fever (66.7%) and cough (52.4%). Compared with the children in Group N, those in Group P had worse clinical characteristics, including those who previously underwent hematopoietic stem cell transplantation (HSCT) or chimeric antigen receptor T (CAR-T) cell treatment (71.4% vs . 28.6%, P=0.005), and those in the myelosuppressive phase (57.1% vs . 4.8%, P<0.001). Most of the children in Group P were treated with more than two types of antibiotics (76.2% vs . 42.9%, P=0.02). The patients treated with Paxlovid within 5 days of diagnosis had a median viral clearance time of 5 days [interquartile range (IQR), 4-8 days], which was significantly shorter than that of the patients who were not treated with Paxlovid (P=0.03). There were no significant differences in the clinical outcomes between the two groups after the propensity score matching (PSM) analyses. Eight patients (19%) had repeat-positive (re-positive) test results. No factor was found to be statistically significant in predicting re-positive test results based on the binary logistic regression analysis. Conclusions: Administering Paxlovid within 5 days of the diagnosis of the SARS-CoV-2 Omicron variant infection in children may effectively shorten the clearance time of the virus, but there is still the possibility the patients may have re-positive test results.