Immune reminisces about a year in COVID-19 immunology, Steph’s receiving the Pfizer vaccine, and answers to listener questions about a challenge study with common cold CoVs, T cell exhaustion, how CD4 T cells control infections, and more.

Immune catches up on COVID listener email, including discussions about long-term COVID, cross-reactive memory to SARS-CoV-2, common mucosal surfaces, the risky business of peptide mega-pools, immunodominant epitopes and much more.

Immune describes the striking loss of germinal centers in lymph nodes and spleen in patients with severe COVID-19, providing an explanation for short-lived humoral immunity and limited somatic hypermutation of antibodies to SARS-CoV-2.