I fail to see why repeated vaccination with updated vaccines is warranted when durability against severe infection was noted: An important finding is the robust and durable protection against severe COVID-19 on reinfection in both pre-Omicron and Omicron eras, with no observed waning in this protection. This distinct pattern suggests the involvement of different immune system components in protecting against non-severe versus severe reinfection. Whereas humoral immunity, mediated by neutralizing antibodies that block viral entry34,35, is the primary driver of protection against non-severe reinfection, it faces intense pressure from viral evolution towards immune escape. Conversely, protection against severe reinfection seems strongly influenced by cellular immunity through memory T cells36,37,38, which appears to be largely conserved37,38, perhaps indicating limited pressure on cellular immunity from the evolutionary forces driving immune escape.