Background: Post-acute sequelae of SARS-CoV-2 infection (PASC) affects patients after recovering from acute coronavirus disease 2019 (COVID-19). This study investigates the impact of SARS-CoV-2 vaccination on PASC symptoms in children in Taiwan during the Omicron pandemic. Methods: We enrolled children under 18 years with PASC symptoms persisting for more than 4 weeks. Data collected included demographics, clinical information, vaccination status, and symptom persistence. We used logistic regression models to compare symptoms in the acute and post-COVID-19 phases and to assess the association between vaccination and these symptoms. Results: Among 500 PASC children, 292 (58.4%) were vaccinated, 282 (52.8%) were male, and the mean (SD) age was 7.6 (4.6) years. Vaccinated individuals exhibited higher odds of experiencing symptoms in the previous acute phase, such as cough (adjusted odds ratio [AOR] = 1.57; 95% confidence interval [CI]: 1.02–2.42), rhinorrhea/nasal congestion (AOR = 1.74; 95% CI: 1.13–2.67), sneezing (AOR = 1.68; 95% CI: 1.02–2.76), sputum production (AOR = 1.91; 95% CI: 1.15–3.19), headache/dizziness (AOR = 1.73; 95% CI: 1.04–2.87), and muscle soreness (AOR = 2.33; 95% CI: 1.13–4.80). In contrast, there were lower odds of experiencing abdominal pain (AOR = 0.49; 95% CI: 0.25–0.94) and diarrhea (AOR = 0.37; 95% CI: 0.17–0.78) in children who had received vaccination during the post-COVID-19 phase. Conclusions: This study revealed clinical features and vaccination effects in PASC children in Taiwan. Vaccination may reduce some gastrointestinal symptoms in the post-COVID-19 phase.

Background: The clinical features and risk factors of post‑acute sequelae of SARS‑CoV‑2 infection (PASC) in children remain incomplete. This study aims to clarify the manifestations and identify predictors of PASC in pediatric patients previously hospitalized for COVID‑19. Methods: We conducted this retrospective cohort study at the China Medical University Children’s Hospital in Taiwan, including 143 children aged 3-18 hospitalized for the acute COVID-19 during the Omicron pandemic from April 2022 to July 2023. PASC was assessed through phone calls, online survey, and in-person follow-ups. Data encompassing demographics, clinical presentations, laboratory results, and acute-phase treatment were collected and compared between children with and without PASC. Each child was assigned total clinical scores based on the acute-phase symptoms and treatment. We evaluated the association of the total clinical scores with PASC among study children. The receiver operating characteristic (ROC) analysis was used to determine the optimal cutoff for total clinical scores, which best differentiated occurrence of PASC. Results: Among the 143 discharged children, 35.7% (n = 51) developed PASC. Children with PASC tended to be older (mean age: 7.6 vs. 6.3 years, p = 0.05) and greater body weight (29.1 vs. 23.7 kg, p = 0.05). PASC children exhibited higher reverse transcriptase-polymerase chain reaction (RT-PCR) cycle threshold (Ct) values (17.1 vs. 14.2, p = 0.04) during the acute phase than those without PASC. There were no significant disparities in other laboratory results, length of intensive care unit (ICU) stays, bacterial coinfections, oxygen supplementation, and medication usage between two groups. Notably, compared to the control group, the total clinical scores were significantly higher in the PASC group (37.9 vs. 31.5, p = 0.02), with an optimal cutoff value of 37.7 yielding an area under the curve (AUC) of 0.70. Conclusions: This study identified a significant proportion of children developing PASC following hospitalization for acute COVID-19. Older age, greater body weight, and larger RT-PCR Ct values during the acute phase emerged as potential risk factors for developing PASC. Moreover, the clinical scoring system constructed in this study may help to predict the risk of developing PASC after discharge.