A small number of people (eight) had signs of previous natural covid-19 infection. Compared with those without previous infection, their antibody and T cell responses after the first vaccine dose were significantly higher (691-fold and fourfold, respectively). The study also found stronger T cell responses in people who had received the AstraZeneca vaccine, with 31% of this group producing detectable T cell responses compared with 12% of the Pfizer-BioNTech vaccine group. The researchers said that the clinical importance of the difference in T cell response was not yet clear, but it could be important when dealing with variants of covid-19....