New study could boost vaccination argument for Merck's Gardasil

A new study finds that Merck’s Gardasil 9 may provide additional protection not included in its official FDA label.

As U.S. doctors and health officials hustle to drive up HPV vaccination rates, a new study suggests Merck’s Gardasil may protect against head and neck cancers, an indication that's not on the vaccine's official list.

Presented by MD Anderson Cancer Center professor Maura Gillison ahead of the annual American Society of Clinical Oncology meeting, the study found an 88% reduction in oral infections for those who were vaccinated. Merck’s latest iteration of the shot, Gardasil 9, is approved to protect against cervical, vulvar, vaginal and anal cancers in females and anal cancers in males, but not for head and neck cancers.

Based on data from 2011 to 2014 from the National Health and Nutrition Examination Survey, the study doesn’t establish a cause-and-effect relationship between vaccination and a risk reduction, according to MD Anderson. But it could add to the case for broader uptake of the shot.

Related: Gardasil posts big Q1 beat to push Merck vaccines to 21% growth

As Gillison notes, no clinical trial has yet tested whether HPV vaccines protect against oral infections. Her study compared infection rates between those who received a shot of an HPV vaccine and those who did not, out of a group of 2,627 young adults aged 18 to 33.

Digging further into the numbers, the investigators didn’t find any infections in vaccinated males, suggesting that vaccination “may be reducing the prevalence of those infections by as high as 100%,” Gillison said in a statement. HPV-related head and neck cancers disproportionately affect males, according to the center, an issue highlighted by actor Michael Douglas back in 2013.

But Gardasil can’t protect those who don’t get vaccinated, and the authors note that uptake rates remain lower than desired in the U.S., particularly for males. Health officials have gone through painstaking efforts in recent years to increase the rate of HPV vaccination, lately leaning hard on the cancer-prevention angle.

Related: CDC aims to jump-start Gardasil uptake with a new two-dose HPV shot schedule

Last year, the CDC changed its recommendation to a two-dose HPV vaccination schedule, down from three doses, in an attempt to boost rates. Aside from that decision, groups including all 69 National Cancer Centers and ASCO have increased their efforts to encourage vaccination as skepticism over the shot has lingered. For its part, Merck aired a TV ad putting the onus on parents to get their children vaccinated.

According to recent figures from the CDC, 63% of teen girls have started the vaccination series, compared to 50% for teen boys.

Related: GSK exits U.S. market with its HPV vaccine Cervarix

Gardasil is a critical growth driver at Merck, turning in $532 million in first-quarter sales for the New Jersey drugmaker, helping to push its vaccines revenues up 21% for the period. Merck now holds close to 100% of the U.S. market, execs reported on an accompanying conference call.

Last year, GlaxoSmithKline pulled its HPV vaccine Cervarix from the U.S., citing “very low market demand.”