Value of my prior publications when changing fields
I've had a somewhat similar experience, having done my Ph.D. in artificial intelligence / cognitive modeling and then later abandoning that area as I have moved into synthetic biology (my other line of research remained consistent, but that's a different story).

The good news is that you're at a perfect time in your career to make a field transition, and that a postdoc or two is the recommended way of doing so.  The bad news is that your prior publications count for pretty much nothing in the new field, and that this is further compounded by the fact that conference publications generally do not count in biomedical fields, only journals.

The reason that your prior publications don't count is simply that they are mostly not relevant evidence of what you can accomplish in the new field.  They are evidence of your fundamental technical skills, and since many of those are transferrable, that has no doubt helped with your current job applications.  A funding agency, however, will generally want a PI with a clear track record of accomplishment, particularly for highly competitive programs like Horizon 2020 (there's likely no problem including you as key personnel for your skills, though).  Likewise, after you've been in the field for a 2-3 years, people will expect you to start having some good journal publications in the new field, and it is these that you will be evaluated on in applying for future jobs, much more than your prior AI work.

Right now, then, the thing to do is buckle down and do good work, which can then fill up the future publication queue.  Making a transition is hard, but can be very rewarding, and all you likely need is a few solid mid-tier journal publications or one really high impact publication and you can bootstrap yourself nicely into your new chosen direction.