If AZ is safe, why not continue with first dozes of AZ and speed up the second dose of Pfizer? Or AZ is safe only when the government wants it to be safe?
They had much larger supplies of Pfizer and Moderna and had more regular delivery schedules. It is an easy decision to focus on them. They set themselves up to have a more reliable second dose scheme if they focus on Pfizer and Moderna first doses, and run out AZ as second doses when more came in.
The decision to pause was also based on the increased and more reliable supply of the Pfizer and Moderna mRNA vaccines and the downward trend in cases.

