Background: The proportion of children and adolescents with COVID-19 had gradually increased according to data reported by WHO. However, there was no meta-analysis of effectiveness and safety of SARS-CoV-2 vaccines in children and adolescents. We aimed to provide investigation-based medical evidence and reference recommendations for children and adolescents in regard to SARS-CoV-2 vaccines. Methods: We systematically searched PubMed, Embase, and Web of Science from inception to 5 January 2022. RCTs and observational studies that examined the effectiveness and safety were included. Results: A total of 13 eligible studies were included for analysis. For the first dose, the effectiveness of SARS-CoV-2 vaccines against SARS-CoV-2 infection and COVID-19 was 88.5% (95% CI:15.7–98.4%, p = 0.033) and 84.3% (95% CI: 66.6–92.6%, p < 0.001) separately. For the second dose, the effectiveness against SARS-CoV-2 infection and COVID-19 was 91.6% (95% CI: 37.8–99.5%, p = 0.083) and 92.7 (95% CI: 82.2–97.0, p < 0.001) separately. Injection-site pain, fatigue, headache, anorexia, and axillary swelling were the top five adverse events after the first dose of SARS-CoV-2 vaccines. Fatigue, injection-site pain, headache, chills, and myalgia/muscle pain were the top five adverse events after the second dose of SARS-CoV-2 vaccines. Conclusions: SARS-CoV-2 vaccines had good effectiveness and safety in children and adolescents. We suggest that children and adolescents should get vaccinated as soon as possible to protect themselves and slow the spread of the pandemic.

ObjectiveTo analyze the relationship between 24‐h movement behaviors and adolescents' physical fitness, with sex difference and age disparity explored specifically.MethodsA total of 135 852 Chinese adolescents aged 13–22 years were included in this cross‐sectional study. Self‐reported 24‐h movement behavioral times, including moderate to vigorous physical activity (MVPA), recreational screen, and sleep, were identified as meeting guidelines based on Canadian recommendations. Physical fitness indicator (PFI) was calculated through sex‐ and age‐specific z scores of body mass index, forced vital capacity, 50 m dash, sit‐and‐reach, standing long jump, body muscle strength, and endurance running, and then classified as: low level (<20th), middle level (20th–80th), and high level (>80th). Mixed effect logistic regression was applied to analyze the association, and interaction terms were constructed to prove the sex and age disparities.ResultsOnly 12.4% of adolescents aged 13–22 years met all three recommendations. The number of meeting guidelines exhibited a typical dose–response relationship with high level PFI (OR = 1.22 [95% CI: 1.19–1.25]), and in detail, meeting MVPA + recreational screen (OR = 2.29 [95% CI: 2.09–2.51]) or MVPA‐only (OR = 2.16 [95% CI: 1.93–2.41]) guidelines were better associated with high‐level PFI. Besides, meeting MVPA‐only guideline was proved with stronger association with high‐level PFI for boys (p‐interaction = 0.005). The dose–response relationship in boys of the number of guidelines met with PFI was stronger in 19‐ to 22‐year‐olds (p‐interaction <0.001) and 16‐ to 18‐year‐olds (p‐interaction = 0.001) than that in 13‐ to 15‐year‐olds.ConclusionThe prevalence of meeting 24‐h movement behaviors guidelines among Chinese adolescents aged 13–22 years was relatively low. It was associated with adolescents' physical fitness, with meeting MVPA + recreational screen or MVPA‐only guidelines bringing greater benefits, and sex difference and age disparity existing.

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