March 13 (Reuters) - Merck & Co ( MRK ) said on

Wednesday it plans to conduct clinical trials testing its human

papillomavirus (HPV) vaccine Gardasil 9 to evaluate the efficacy

and safety of a single-dose regimen compared to the approved

three-dose regimen.

The company said it plans to conduct two separate trials

testing Gardasil 9 in men and women 16-26 years old to examine

whether a single dose of the vaccine provides comparable

long-term protection when compared with the approved three-dose

regimen.

The large, multi-year trials are expected to start

enrollment in the fourth quarter of 2024, according to Merck ( MRK ).

The drugmaker also plans to begin human trials for an

experimental HPV vaccine in the fourth quarter that is designed

to offer broader protection by targeting multiple HPV types.

The U.S. Food and Drug Administration first approved

Gardasil 9 in 2014 to prevent certain cancers, including

cervical, vulvar, vaginal and anal cancers, and diseases caused

by nine variants of HPV.

Gardasil 9 is now approved for use in women and men aged 9

through 45 years.

HPV causes about 36,000 cancer cases in both men and women

every year in the United States, according to government data.