there is plenty of genetic evidence linking neanderthal genetic features to outcome of disease and genetic infirmity, as well as outcome of covid infection, primarily to do with interferon production and signaling, as well as receptor domains, these are heteroallelic as well, so strong neanderthal heritage with respect to population at large may provide a protective allele, or a predispositional allele.

https://www.sciencemag.org/news/2020/12/neanderthal-gene-fou...

https://www.biorxiv.org/content/10.1101/2020.12.11.422139v1

https://www.nature.com/articles/s41586-020-2818-3

https://www.news-medical.net/news/20201215/Neanderthal-gene-...

https://www.nejm.org/doi/full/10.1056/NEJMe2025501

https://www.pnas.org/content/118/9/e2026309118

https://www.biorxiv.org/content/10.1101/2020.12.11.422139v1