Since vaccines have been available, I have received my first and second doses, as well as a booster shot. Vaccines work by exposing our immune system to the virus’s spike protein, and setting in motion an early arsenal of antibodies and specific T cells. These leave behind memory cells, which can hold out for years and spring into action to prevent reinfection. Although covid-19 vaccines still protect against the most severe forms of the disease, every time a new variant emerges, we scientists frantically try to figure out, from real-life data, whether it can evade vaccine protection. We cannot predict when the efficacy of the vaccine will wane, because we do not observe the gradual evolution of the virus, in which emerging lineages add new mutations to their predecessors; The Omicron variant, which is prevalent today, bears little resemblance to Delta, which spread widely last year
Natural infection does not offer long-term protection, and vaccine-induced immunity, which is more potent, needs a booster to protect against variants. As a result, if I had previously contracted a variant, but reacted well, I am not convinced that I can be immune to the next one. In fact, people report different symptoms after different cycles of infection: over the course of subsequent infections, some feel better and others worse.