Demographics of the population, when countermeasures were rolled out, how severe those were, reporting errors, reporting standards (and changes to those standards as the pandemic progressed), how wealthy / healthy the country is, how much IC capacity they had relative to the size of the population, whether they had a pandemic plan already in place, previous experience with pandemics, initial number of infections prior to planned approach, temperature, humidity, culture of handshakes, prior mask wearing, genetics and so on. This is going to be a very complex problem to get a grip on in such a way that the model does not end up to fit the available data (in other words: that it would not have much in terms of predictive ability).