Here is a recent one: https://www.biorxiv.org/content/10.1101/2020.12.18.423358v1 No peer review yet, and not in-vivo. But they could show in vitro that antibodies created against the "other end" of the spike protein (the one attached to the virus) make it easier for the spike protein to bind to ACE: > Here, we screened a series of anti-spike monoclonal antibodies from COVID-19 patients, and found that some of antibodies against the N-terminal domain (NTD) dramatically enhanced the binding capacity of the spike protein to ACE2, and thus increased SARS-CoV2 infectivity The common vaccines all create the whole spike protein, including the NTD, so that the protein can fold into its natural shape. Enhanced binding is one of maybe 5 different forms of ADE. Others are e.g. infection of cells that are not affected if antibodies are not present, destruction of immune system cells and so on. This could happen with an infection too, not only with vaccination. But there are theories that the quality control (suppressing the bad antibodies and promoting the neutralizing ones) works better in a natural infection compared to the pseudo-infection caused by a vaccine.