medical admissions

How much emphasis does oxford place on research in selection of applicants for interview?

You're not expected to have done original research before, that's something for university and beyond. 17-18 year olds are not doing meaningful research while they're still at school. There's a reason people spend years doing a PhD.

That's good to know. I am a bit worried because I have not done any EPQ and taken only 3 subjects at A level. Given that all applicants for oxford are of very high caliber would they give preference to someone who has shown some kind of research ( not the Phd level obviously) over those who have not in selecting for interview.

Not really. Oxford are trying to select candidates that will perform well at university. Not everyone has had the opportunity to do research at this stage, and you're not expected to do any without any formal education about how to do so. It would unfairly disadvantage certain applicants over others, and medicine is already dominated by people from more affluent backgrounds.