Not that I can tell (EDIT: They did, see comment further down) This seems to be research release by PR, not a published study. Although even if they adjusted for prior infections they should still be comparing comparable time periods. It is really odd if they didn't, and odd if they did do it but the results weren't included in the release. The initial 2020 wave is a reasonable baseline, but not a good measure of relative risk factors between variants right now especially because 2020 didn't include Delta.