Merck's Gardasil 9 offers at least 6 years of cancer protection, data show

A large-scale phase 3 study shows that Gardasil 9's efficacy against certain HPV-related cancers and diseases can last up to six years.

Merck’s Gardasil 9 has come to dominate the HPV vaccine market, and a new, large-scale, phase 3 study that shows its protection against certain cancers lasts six years will only serve to strengthen its case.

The study enrolled 14,215 girls and women 16 to 26 years of age. At six years after the first dose, Gardasil 9's efficacy against cervical, vulvar and vaginal cancers related to HPV 31, 33, 45, 52, 58—five additional HPV types above the four covered in the original Gardasil vaccine—ranged from 90% to 98%.

Protection against types 6, 11, 16 and 18 is similar between Gardasil and Gardasil 9, as inferred from noninferiority comparisons.

Antibody responses to all nine HPV types targeted by Gardasil 9 persisted through five years, the study found. Researchers are following up with the patients for an additional 10 years to evaluate the vaccine’s efficacy over a longer period.

RELATED: Merck's Gardasil preps for head-to-head with GlaxoSmithKline’s Cervarix in China, with big sales targets ahead

Gardasil 9 protects against HPV types that cause about 90% of cervical cancer cases, 90% of genital warts cases and about 80% of high-grade cervical lesions worldwide. The shot can also protect against around 90% of HPV-related vulvar cancers, vaginal cancers and anal cancers, research shows.

Despite the benefits, health officials are still working to improve vaccination rates. A recent CDC tally found that the HPV vaccination rate is growing slowly in the U.S., but given that only 43% of teens had completed the schedule, the agency says there’s still work to be done.

Since Gardasil won its first regulatory approvals in 2006, the Merck franchise has almost monopolized the HPV vaccine market, reeling in $2.17 billion in 2016 sales compared with £81 million (about $107 million) for GlaxoSmithKline's Cervarix. The two companies are set for a competition in China, a lucrative market, after GSK left the U.S. with its shot.

A recent study found that HPV vaccination could also be used to fight head and neck cancers, though that's not an official indication.