High single-dose efficacy of Pfizer vaccine against SARS-CoV-2 in older adults

In British Columbia (BC), Canada, vaccination against coronavirus disease 2019 (COVID-19) began with the Pfizer/Moderna mRNA (messenger ribonucleic acid) vaccines began with nursing home residents and frontline healthcare workers. These are known to have a high protective efficacy of 92-93% after a single dose, but this data comes from younger and healthy adults, for the most part.