To answer that question you need to dive into the original data set (if you want to see yourself: Search ONS death by vaccination status, in the .xlsx it's shee

To answer that question you need to dive into the original data set (if you want to see yourself: Search ONS death by vaccination status, in the .xlsx it's sheet 'Table 4'). There is a reason why the person who made the chart started with 19-Mar-2021: There aren't enough deaths before. Even for the 21-Mar data point it's only 5 deaths! Luckily ONS does provide confidence intervals (column J, K). There is even a marker in the sheet called 'u' to highlight unreliable data due to small numbers. But whoever made the chart was not interested in either (why?). While we are already in the full data set, note that the death rate for the unvaccinated group is appr. 4.0 (!) in Jan 2021. There might also be another reason (hypothetical based on anecdotes): The very first to be vaccinated in the 10-59 group were likely nurses and doctors.