Since the start of the pandemic we have studied cohorts across several countries to evaluate immunity at the level of antibodies, neutralisation and B and T cell memory to understand differential immune patterns due to vaccination and infection. At this stage in the pandemic, immune imprinting due to different exposures (different vaccines, timings and numbers of doses overlaid by different infection episodes with diverse variant sequences) means that people have diverse immune repertoires, with associated implications for immunity to new variants. In this context it has become considerably more challenging to define true correlates of protection. A pressing, related challenge is to define immune parameters associated with the diverse symptom profiles of Long Covid.