Oct 31 (Reuters) - Merck & Co ( MRK ) beat Wall Street

estimates for quarterly earnings on Thursday on strong sales of

its blockbuster cancer treatment Keytruda, but said weak demand

for its Gardasil vaccine in China is likely to carry over into

2025.

Gardasil, which prevents cancers caused by the human

papillomavirus, has been one of Merck's ( MRK ) top growth drivers aside

from Keytruda and much of its international growth has come from

China.

Merck's ( MRK ) shares were off 4% in morning trading after

reporting that the vaccine's sales fell 11% to $2.31 billion in

the quarter, missing the average analyst estimate of $2.46

billion, according to LSEG data.

"It is both a demand issue driven by the economy, some

impact on promotional activity we think related to concerns

about anti-corruption, as well as continuing adjustment of

inventory levels in the marketplace," Chief Executive Rob Davis

said of Gardasil's China sales in an interview.

"Ultimately, what we have to do is drive demand."

The company expects Gardasil shipments to China in the

fourth quarter to be similar to the third. It had similar issues

with Gardasil in China in the second quarter.

Beijing has been running a campaign targeting bribery of

doctors that disrupts business and scuttles hospital deals with

international pharmaceutical companies.

Merck's ( MRK ) overall sales in China fell 40% to $996 million in

the third quarter from $1.67 billion a year ago.

Davis said Merck ( MRK ) believes it still has a significant

long-term opportunity for Gardasil in China with a meaningful

population of women who could receive the vaccine.

"This isn't going to be solved next quarter. It's going to

take us through probably 2025," the CEO said of Gardasil's

issues in China on a call to discuss the results.

Merck ( MRK ) has an opportunity to generate $2 billion to $3

billion from Gardasil sales in China, with a potential expansion

to men being a key growth driver, Davis said.

Gardasil is not the only vaccine that has been hurt by

weakness in China. GSK said on Wednesday that sales of

its shingles vaccine Shingrix fell in the largest Asian economy.

Sales of Keytruda, the world's top-selling prescription

medicine, rose 17% to $7.43 billion in the quarter, beating Wall

Street expectations of $7.20 billion.

Merck's ( MRK ) overall sales of $16.66 billion topped analyst

forecasts of $16.45 billion.

Merck ( MRK ) posted third-quarter earnings of $1.57 a share, down

from $2.13 a share a year ago due to costs from acquisitions.

Analysts on average expected earnings of around $1.50 a share.