While every age group had similar rates of breakthrough cases, death rates varied more drastically by age. Unvaccinated seniors were the most likely to die from COVID of any group. Still, vaccinated people 80 and older had higher death rates than unvaccinated people under 50.

The ratio of case rates declined somewhat in the summer, to six times as high for the unvaccinated in August from about 11 times as high in mid-June, giving scientists reason to believe that the vaccine’s protection against infection might be waning slightly. The ratio for deaths has been flatter over time for all but the oldest age groups, an indication that vaccine protection against death is holding strong.