Fauci co wrote a paper on it.

The work presents complementary lines of evidence from the fields of pathology and history of medicine to support this conclusion. "The weight of evidence we examined from both historical and modern analyses of the 1918 influenza pandemic favors a scenario in which viral damage followed by bacterial pneumonia led to the vast majority of deaths," says co-author NIAID Director Anthony S. Fauci, M.D. "In essence, the virus landed the first blow while bacteria delivered the knockout punch."

https://www.nih.gov/news-events/news-releases/bacterial-pneumonia-caused-most-deaths-1918-influenza-pandemic

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2599911/