(Reuters) - UnitedHealth Group Inc said on Tuesday it expects minimal impact to its margins if the rebate system is overhauled but investors remained concerned about the impact of the Trump administration’s proposal to end discounts from drugmakers.

FILE PHOTO: Traders work at the post where UnitedHealth Group is traded on the floor of the New York Stock Exchange (NYSE) in New York, U.S., January 31, 2018. REUTERS/Brendan McDermid/File Photo

Shares of the company fell 4 percent and dragged down those of rivals Anthem Inc, Centene Corp, Humana Inc and Cigna Corp.

“It goes back to the political pressure on the managed care area,” Thomas Martin, senior portfolio manager at GLOBALT Investments in Atlanta said.

“It remains a wild card even though they are proving that their business model is good and are producing good results.”

The healthcare sector has come under pressure after the U.S. government in January proposed a rule that would overhaul the use of drug company rebates in government-run healthcare plans.

Adding to investor concerns, U.S. Senator Bernie Sanders recently unveiled the latest version of his “Medicare-for-All” plan that would eliminate private insurance and shift all Americans to a public healthcare plan.

UnitedHealth Chief Executive Officer David Wichmann said some proposals being discussed represent a “wholesale disruption of American healthcare” that would impact the economy and jobs without improving patient access.

On the potential impact from the proposed change to the rebate rule, the company said discounts they currently receive are mostly passed on to clients.

“Ninety percent of what we manage is generic (drugs) with no rebates,” said John Prince, a senior company executive.

“Within our total client base, 98 percent of our discounts are passed on to our clients.”

Analysts said that despite the recent slump in shares, fundamentals of the industry are still on track.

“But a negative sentiment around the sector is, in the short-term, more than offsetting what we see as a continued positive fundamental trajectory for UnitedHealth,” Stephens Inc analyst Scott Fidel said.

UnitedHealth on Tuesday raised its full-year adjusted earnings forecast to between $14.50 and $14.75 per share from its prior view of $14.40 to $14.70.

Optum, the company’s fastest-growing unit which houses its pharmacy benefits business, brought in sales of $26.36 billion in the quarter, a jump of nearly 12 percent from a year earlier due to higher prescription volumes.

The company reported adjusted earnings of $3.73 per share, beating estimates of $3.60 per share, according to IBES data from Refinitiv.

Total revenue rose 9.3 percent to $60.31 billion, ahead of estimates of $59.71 billion.