I was down on the AZ Vaccine because it is only effective for 4 months...as it turns out most other vaccines are only effective for 3 to 4 months....I have questions regarding the Pfizer vsaccine. Shouldn't be a problem though as the DR hasn't purchased enough to give everyone two doses of that vaccine. Getting only one dose is questionable even if the second dose is of a different vaccine. At this point it seems to make more sense to wait for the Oxford Astra Zeneca vaccine to arrive in sufficient quantity to be administered as intended.
But I would not take a second dose from a different vaccine; just based upon the formulae which would have to coincide with the first dose
Just my opinion of course.