Health insurer Centene Corp. shocked investors this week when it withdrew its profit outlook on rising risks from Affordable Care Act plans.   

The company appears to have been badly caught off guard by the impact of US government actions. It’s an ominous sign for insurers, whose purpose is to price for risk but have lately been blindsided by it.   

Shares of Centene dropped more than 40% on Wednesday, the biggest one-day drop since its initial public offering in 2001. Other insurer stocks including Molina Healthcare Inc. and Oscar Health Inc. and Elevance Health Inc. also sank by double digits.   

For more on the fallout, Paul Sweeney and Norah Mulinda speak with Glen Losev, Bloomberg Intelligence Senior Healthcare Analyst.