CD40LG and infection: The early seroconversion of IgM against SARS-CoV-2 was reported at 3–5 days, and the level can last for more than 1 month, while IgG against SARS-CoV-2 may be detected after 8 days.202,203 Notably, many reports on serum antibody levels in SARS-CoV-2 patients indicate that IgM expression was observed concurrently with IgG expression.204–207 Long et al. conducted a large multicenter study and found that the median seroconversion of both isotypes was recorded on day 13.208 Udugama et al. found that antibody responses to infection took days to weeks to be reliably detectable.