A potential advisor asked me for abstracts, manuscripts, posters, presentations, etc. but I just graduated from a Master's Degree in the field of biomedicine/biological sciences in Spain and here most Masters are very coursework-oriented so I don't have any of that, and as far as I know it's not very common for Master students here to have many publications or poster presentations. I just produced two Theses, one for my Bachelor's final project and other for my Master's final project, which will be published as an article but it hasn't even been submitted yet. I was a bit surprised because I don't know if it's very common in the US to have papers published and have presented at conferences before even starting a PhD.
I would expect applicants for a PhD program in biomedical/biological sciences in the US to have research experience as an undergraduate (it's less common to have a master's degree but some will).
That research experience is likely to come with at least poster presentations, and preferably published or at least submitted manuscripts (hopefully available as preprints, which has become more common in biology and medicine than just a few years ago). I would not necessarily expect these posters/publications to be first-authored, but the applicant should have enough understanding of the projects that they could present on them in their entirety by themselves.
A thesis based on research will count for a bit, too, but theses based on coursework or literature review not as much: the point is to show preparation and aptitude for a research career.
There might be a lot of otherwise good applications from people without those qualifications, but too many other good applicants will have them, and since there's little else to truly differentiate candidates that will matter a lot.
I've worked with undergrads and recent graduates applying for graduate school, and in multiple cases the applicants without a publication record applied unsuccessfully for PhDs whereas a year later with a publication the same students had multiple offers to choose from. That doesn't mean I wouldn't suggest applying without publications, though, just that it counts for a lot. You necessarily only have what you have, so if asked that's what you'll have to provide. As far as I can tell there has been a big shift from when I was applying for graduate school only ~15 years ago towards more extensive CVs from graduate school applicants.