It changed over time. Almost everyone vaccinated who was 40 and under and boosters have been done with Pfizer/Moderna. The adenovirus vaccines were used mainly

It changed over time. Almost everyone vaccinated who was 40 and under and boosters have been done with Pfizer/Moderna. The adenovirus vaccines were used mainly early on for higher age groups and at-risk groups getting initial doses. In any case, the virus in the Oxford vaccines couldn't replicate and was a chimp virus that people hadn't been exposed to previously, so they would obviously notice if that specific virus started circulating.