The vaccine for human papillomavirus (HPV), a sexually-transmitted virus spread to 14 million new Americans each year and causing more than 30,000 cancers every year, has successfully slowed the spread of the STD among the youngest segments of the population over the last decade-plus.

Now the vaccine has been approved for an older segment of the population—ages 27 through 45, according to a U.S. Food and Drug Administration announcement Friday.

The population-level effort is an attempt to reduce the number of infections, and boost immunity among the “herd,” according to health officials.

“Today’s approval represents an important opportunity to help prevent HPV-related disease and cancers in a broader age range,” said Peter Marks, the director of the Centers for Biologics Evaluation and Research at the FDA.

The first Gardasil vaccine was approved by the FDA in 2006. Its first version covered four HPV types that were the most-common cancer causers among the 100 strains known circulating in the population. The updated Gardasil 9, covering nine strains, was approved by the FDA in 2015, and was approved for both sexes between the ages of nine and 26.

Statistics show that the nine strains of the virus covered by the Gardasil 9 vaccine can prevent more than 90 percent of the cancers of the cervix, anus, penis and throat.

Prior to this FDA approval, a Gardasil study undertaken among 3,200 women who were between 27 and 45 were monitored for an average of more than three years. The conclusion: the shots were 88 percent effective in preventing viral symptoms of persistent infection, including genital warts, precancerous lesions of the vulva and vagina and cervix, and cervical cancer. 

Australia is in many ways leading the world in HPV vaccination rates. The country has a fully-funded national program that began in 2007. In 2016, the full-course, triple-dose coverage rates for children turning 15 was 78.6 percent for girls and 72.9 percent for boys.

A study last week in The Lancet projects “cervical cancer elimination” in the country by the mid-21stcentury. (The current rate of the disease is seven in 100,000 women, and by 2066 they project it to fall to one in 100,000, due to the national vaccine and screening programs.)

The U.S. vaccination rate is far lower. According to CDC data, just half of all adolescents were completely inoculated with all the doses of Gardasil as of last year—although about 66 percent of those aged 13 to 17 had received the first dose. That first-dose rate has increased by 5 percentage points each year, from 2013 to 2017, according to the federal health agency. Some of the morbidity statistics show that vaccine rates in American rural areas is significantly lower than urban areas.

The FDA approval of the Gardasil vaccine for adults does not change epidemiological guidance for population-level inoculations. In fact, the CDC has not yet changed its recommendation to include adults up to 45.