We analyzed 15 cytokines related to cytokine release syndrome in lung development of Rhesus monkeys and found that compared with those in neonates, levels of proinflammatory cytokine tumor necrosis factor α and IL-1β were significantly elevated in adults, and levels of IL-6 were comparable between adults and neonates, which might in part explain the less severe inflammatory responses in pediatric COVID-19 patients compared with adults. Here, TNF is linked to COVID-19.