March 7 (Reuters) - The hack at UnitedHealth's ( UNH )

tech unit has led to uncertainty around when high medical costs

for health insurers will subside as the cyberattack leads to

prolonged delays processing insurance claims, Wall Street

analysts said.

While UnitedHealth ( UNH ) said most of its pharmacy services

operations, which were also taken down in the Feb. 21 attack,

are expected to come back online as early as Thursday, the

company has said its medical claims network will take longer to

be restored.

United's Change Healthcare unit is a vital lynchpin in the

complex U.S. system for making and clearing insurance claims,

connecting providers to not just UnitedHealth ( UNH ) but also to CVS

Health's ( CVS ) Aetna, Elevance, Humana, and

others.

"There could be effects on cash flow and more uncertainty

around medical utilization estimates going forward," said

Morningstar analyst Julie Utterback.

UnitedHealth ( UNH ) and its rivals carefully monitor insurance

claims, targeting to spend as close to 80% or 85% of the

premiums they take in on medical services, as required under the

U.S. Affordable Care Act popularly known as Obamacare.

Wall Street analysts have not yet given an estimate for the

size of a financial impact to UnitedHealth ( UNH ) or other insurers for

the ransomware attack. The company is believed to have paid the

hackers $22 million in cryptocurrency.

Shares of UnitedHealth ( UNH ) and rivals have been under pressure

since late November, when the industry bellwether said a

late-year increase in medical care among older adults had led to

elevated medical costs.

Humana and CVS Health ( CVS ) have said they were not sure how long

the trend of higher costs would last.

Investors had been hoping for evidence that medical services

spending had returned to more normal levels, but the disruption

to claims processing likely means that will be delayed until the

companies report second quarter earnings later this year, said

BofA Global Research analyst Kevin Fischbeck in a research note.

Citi analyst Jason Cassorla said in note on Wednesday that

he "wouldn't be surprised" if new patient healthcare

appointments were impacted by the disruption to the claims

processing system.

Most analysts expect a limited hit to UnitedHealth's ( UNH )

earnings from the hack, given that Change accounted for about

13% of the company's total operating profit. United is expected

to earn $6.69 per share in the first quarter, according to LSEG.

UnitedHealth ( UNH ) has said hackers who identified themselves as

the "Blackcat" hacking gang perpetrated the attack.

Cyberattacks like this tend to be "short-term blips" for the

companies that have been hacked, said Morningstar's Utterback.

"However, the longer this situation drags on and materially

affects its customers' operations, the more impact it will

probably have on UnitedHealth's ( UNH ) reputation and business in the

long run," she said, "including customer switching."