I was planning on waiting till my second AZ was available at 12 weeks but doing some reading and found this.
If I am reading this right it says that AZ followed by Phizer is 3.9 times better at combatting variants than getting two shots of Phizer.
A recent study from Germany released June 1 as a
non peer-reviewed preprint adds additional information around mixing and matching AstraZeneca and Pfizer vaccines. This preliminary data included 26 individuals, ages 25 to 46, who were administered AstraZeneca as their first dose of vaccine, followed by a second dose of Pfizer given eight weeks later. Neutralizing activity was 3.9 times greater against the alpha (B.1.1.7) variant and similar against the delta (B.1.617.2) variant compared to neutralizing activity seen in people who received two doses of Pfizer vaccine. No safety concerns were noted.
https://nationalpost.com/news/canad...-it-again-or-choose-pfizer-or-moderna-vaccine
Also reading that Moderna is as good a substitute for Phizer.
https://www.ctvnews.ca/health/coron...-good-as-pfizer-when-mixing-with-az-1.5471400