Lung viral titers (Fig. 5c), lung histopathological analysis (Fig. 5d), and gene expression of type I interferon signaling (Ifit and Rsad2) and Il6 as drivers of pathological pulmonary responses after SARS-CoV-2 infection61 (Fig. 5e) further confirmed the reduced SARS-CoV-2 infection in aged mice immunized with RBD-NP formulated with CMS:O/W adjuvant. Here, IL6 is linked to COVID-19.