The whiplash over a new potential flu vaccine from Moderna, which went from rejected to approved for review in a matter of days, has illustrated a new reality plaguing the Cambridge biotech company and other vaccine makers: Political headwinds are now an unavoidable and unpredictable factor in their business model.

The FDA refused to review Moderna’s application for a new flu vaccine, the company said yesterday. It’s a surprising decision that could raise concerns about the agency’s posture toward drug companies and, of course, the administration’s policies on vaccines overall.