Hot off the Presses: Positive Immune Response is More Robust to SARS-CoV-2 Than Previously Thought

T cell memory and mucosal immunity develop in asymptomatic as well as mildly symptomatic individuals infected with SARS-CoV-2. Anti-CoV-2 antibody was detected in serum and saliva, with peak IgG levels by 16-30 days after disease onset. Whereas anti-CoV-2 IgA antibodies rapidly decayed, IgG antibodies remained up to 115 days in both saliva and serum (https://www.medrxiv.org/content/10.1101/2020.08.01.20166553v1 and https://www.medrxiv.org/content/10.1101/2020.07.18.20155374v1). Those recovered from mild COVID-19 developed SARS-CoV-2-specific IgG antibody and neutralizing plasma, as well as virus-specific memory B and T cells which persisted, and in some cases increased over three months following symptoms’ appearance. Furthermore, the SARS-CoV-2-specific memory T and B cells exhibited potent antiviral immunity: memory T cells secreted IFN-γ and increased in number after second viral exposure, while memory B cells expressed receptors that neutralized virus and led to expressed neutralizing antibodies (https://www.medrxiv.org/content/10.1101/2020.08.11.20171843v2). Most importantly, SARS-CoV-2-specific T cells were detectable in antibody-seronegative exposed family members and recovered individuals with a history of asymptomatic and mild COVID-19. The data shows that SARS-CoV-2 induces robust, broad and highly functional memory T cell responses, implying natural exposure, vaccination, or infection may prevent reinfection and severe COVID-19 (https://www.cell.com/cell/pdf/S0092-8674(20)31008-4.pdf?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0092867420310084%3Fshowall%3Dtrue .