Wasn't there research indicating and a reduction in vitamin D lead to an increased risk of death, but then it was shown that it's not that the vitamin D was the cause of the increased risk, rather it was a proxy for people who were unable to protect themselves from covid because they desperately needed to work?

edit: I'm looking for sources currently, and seeing a lot on the poor Covid prognosis predictions with low vitamin D and a handful of papers indicating that poverty tends to lead to vitamin deficiencies, but not something that connects the two. Additional sources from folks that can clarify would be appreciated.