ということです seems to be something specific to formal writing and news reporting. I encounter it a lot in books on history or philosophy and generally in a context when the opinion of someone, who's not necessarily been specified, is quoted.
I've struggled myself with how to translate it when I run across it in a text, but generally it doesn't seem to translate well. Japanese is very sensitive to how we get the information we're passing on: did we observe it ourselves or did we learn from someone else.
My guess would be that ということです doesn't necessarily indicate a particular source. It could be a conclusion reached by the impression you get from several different sources. In the article you're quoting it's perhaps something gleaned from what the Covid Research Groups have published. I think it's the lack of specificity of 研究班 that leads to this vague citation through the expression ということです