That's true, UtW. I had forgot that AZ was a two dose system but they were holding off on doses, which is why I think I thought it was a one dose deal.
Here in the States you normally actually can pick your manufacturer, sometimes by choosing where you go to get the shot. Some pharmacies, stores, or health departments are doing one or the other. And now that Biden has opened up the vaccines, you can go anywhere to get it and not on a rollout by your state's department of health. Now with more availability, you can be more "choosy".
I chose a place that gave Moderna which was HyVee, a grocery store/pharmacy chain in the US. It was before it was generally available. At that time they were still following the state department of health's rollout. I qualified under Phase 1c, which is those under 65 with preexisting conditions. Same with my dad. My mom got hers early. She works in a school and was considered an essential worker, so she actually got hers before Phase 1b, which was seniors/above age 65. She was in the Phase 1a here in IL. Gov. Pritzker did a good job with the rollout but I'm glad it's generally available.
I'm not sure that I'm convinced that waiting longer between doses is a good idea or that it's better than the one-month cycle of Moderna and Pfizer if I'm being honest. I think that one shot does NOT offer enough protection, especially if that shot was built for a two dose administration. That seems like an awfully long time to wait with a half-strength dose. Is it better than nothing, of course, but I'd be concerned that for the at-risk people, that wouldn't be enough to keep them from getting ill. I think that seeing how people react to their second doses of Moderna and Pfizer, they are building enough of an immune reaction since there is significantly more side effects after the 2nd administration of the vaccine. I do think the people who have more signs of feeling under the weather the day after the second shot means that they built a stronger reaction than those who got away with nothing more than a sore arm. Only time will tell but I do have a lot of confidence in the mRNA vaccines.