which we refer to as the 'adjusted reproduction number'the adjustment referring to the correction of the effective reproduction number for the proportion of the population that are susceptible. When there is no social distancing, R A ðtÞZ R 0 . Our goal is to estimate how much of the variation in the reproduction number exceeds that which can be attributed to the build-up of immunity, and to attribute that to social distancing. We define s min to be the lowest value of s(t) obtained from the analysis, corresponding to the point of greatest social distancing.