The multiple streams approach (MSA) emphasises that problem indicators, which refer to numeric measures of a problem, are an important determinant of policymaker attention. However, few studies empirically examine the relationship between indicators, agenda setting and policy change. This study fills this void by modelling the extent to which indicator change induces agenda activity in emerging disease domains. It shows that the rate of indicator accumulation – how quickly indicators amass – is a predictor of agenda activity. Although rapid accumulation almost always captures policymaker attention, policy change is more likely when indicators slowly amass and provide ample time for political mobilisation.