We describe the projection of the severity rate and case fatality rate associated with COVID-19 infection for the sixth infection wave in Tokyo. Combining the data from the previous infection wave with early evidence on the Omicron variant from other countries, we projected a large decline in both severity and case fatality rates from the fifth wave to the sixth wave in early January 2022—from 0.66% and 0.31% to 0.15% and 0.09% for the severity rate and the case fatality rate, respectively. The actual severity rate was lower than our projection—0.04% versus 0.15%—whereas the actual case fatality rate was about the same as our projection—0.11% versus 0.09%. Our real-time analysis shows that a simple but sensible methodology can be a useful tool in predicting a large shift in the severity and case fatality rate during a pandemic.