There was not widespread serology testing but subsequent analysis has the WHO pegging the fatality rate at about 3% (as opposed to the 10% from the time of the outbreak itself).
We didn't really shut SARS down so much as it seemed to have shut itself down, conventional epidemic control measures were enough to contain it and it was not quite easily transmissible enough to sustain itself in the wider population without being allowed to gain a real foothold undetected first.
That last point would be why you would not expect (and I would think it is impossible) to find that at the end of the day COVID-19 will be anywhere near as deadly as SARS. We have strong evidence that it takes truly extraordinary measures to suppress this new virus at a rate that will in fact eliminate it from a population when compared to SARS. SARS simply didn't spread that widely because if it did that would directly contradict the relative ease of its containment.
We didn't really shut SARS down so much as it seemed to have shut itself down, conventional epidemic control measures were enough to contain it and it was not quite easily transmissible enough to sustain itself in the wider population without being allowed to gain a real foothold undetected first.
That last point would be why you would not expect (and I would think it is impossible) to find that at the end of the day COVID-19 will be anywhere near as deadly as SARS. We have strong evidence that it takes truly extraordinary measures to suppress this new virus at a rate that will in fact eliminate it from a population when compared to SARS. SARS simply didn't spread that widely because if it did that would directly contradict the relative ease of its containment.