At least one of the researchers (Paul E. Schulz) disqualifies this study, his disclosure:
"Consulting Fees:
Occasional advisory panels for Lilly, Acadia, and Biogen.
Lecture Fees:
Occasional disease state education talks for Lilly, Acadia, and Biogen.
Patents/Royalties
I serve as an expert witness for medical malpractice cases and other types of cases. None related to this paper. Not sure where to put this, but i am on about 12 NIH grants, none related to this study. And i have about 12 treatment trials funded by many pharmaceutical companies, including Lilly, Acadia, Biogen, Roche, UCB, etc. None are related to this paper, in my opinion."
And that's just one, who is even admitting anything, the others can be funded through various shell companies which looks at first unrelated to pharma and claim they have nothing to disclose. You won't bite hand that's feeeding you.
I take any research pushing vaccination (especially something like flu vaccines which are pretty much placebo with 10-60% efficacy if you are lucky [1] [2], if not 0%) with big grain of salt nowadays after our experiences with these "safe and effective" COVID vaccines, which were proven to be not so safe and hardly effective at all.
[1] https://www.science.org/content/article/why-flu-vaccines-so-...
[2] https://www.ecdc.europa.eu/en/seasonal-influenza/prevention-...