In many countries, deaths from COVID-19 were highly concentrated among care home residents during the initial wave of the pandemic. Care home residents may have faced higher risks of exposure and infection than the general population of older people. Once infected, residents may have been more likely to succumb to this disease as they were both older and frailer than the general population of older people. This study presents a quantified assessment of these factors in Belgium and in England and Wales. In doing so, this paper applies the Das Gupta decomposition method to explain the contributions of these three factors to the observed differences in mortality rates from COVID-19 between older people residing in care homes and older people living at home. According to these estimates, older people residing in care homes were 36 times more likely to die in Belgium and were 23 times more likely to die in England and Wales from COVID-19 than older people living at home during the initial wave of the pandemic. Decomposition of the differences in the mortality rates of these populations in Belgium and in England and Wales showed that the two key determinants were the greater underlying frailty of older people in care homes (accounting for 46% of the differences in Belgium and 66% of the differences in England and Wales) and the higher infection prevalence of older people in care homes (accounting for 40% of the differences in Belgium and 26% of the differences in England and Wales).