At the time of the assessment of the sanitary measures taken to fight the crisis, we have analysed the testing and vaccination following the grid well known in health economics: the law of diminishing returns. In the first phase, the returns are positive and increasing, the increase in benefits being faster than the increase in costs. In the second phase, returns are still positive but decreasing, with costs increasing faster than benefits. In the third and last phase, the returns become negative, with benefits decreasing despite an increase in costs. Both testing and vaccination, which were very beneficial at the beginning of the crisis, progressively followed a trajectory of diminishing returns with the extension of the measures to wider populations (asymptomatic or young persons), or for example with the emergence of the Omicron variant.