March 25 (UPI) -- Introduction of the human papillomavirus, or HPV, vaccine in the United States has led to a more than 80% decline in infections nationally since 2003, according to data released Thursday by the Centers for Disease Control and Prevention.
Over that period, HPV infections among sexually experienced females age 14 to 19 declined by 97% in those who had received the vaccine and by 87% in those not vaccinated, the data showed.
Among sexually experienced and vaccinated women age 20 to 24, cases of HPV dropped by 86% in those vaccinated and by 65% in those unvaccinated.
The declines among females who had not received the vaccine, which was approved by the U.S. Food and Drug Administration in 2006, indicates that the shot may provide indirect protection due to decreased transmission of HPV in the population, the CDC said.
However, "the COVID-19 pandemic has the potential to reverse gains made in HPV vaccination coverage in the United States, as indicated by lower adolescent vaccine orders in 2020," the agency researchers wrote.
"Efforts are needed to increase HPV vaccination to maintain the substantial progress of the vaccination program," they said.
At 43 million infections in 2018, HPV remains the most common sexually transmitted infection in the United States, even with the vaccine, and there is no cure, according to the CDC.
Symptoms of HPV include warts on the genitals or surrounding skin, and it has been linked with cervical and other cancers.
The CDC has recommended that females receive the HPV vaccine at age 11 or 12 since the shot -- called Gardasil and manufactured by Merck -- was approved by the FDA.
Males of the same age have been advised to get the vaccine since 2011, and "catch-up" shots for those not yet inoculated are recommended up to age 26.
The report released Thursday compared HPV infection rates nationally from 2015 to 2018, the most recent year for which data are available, to the period between 2003 and 2006, or immediately before the first HPV vaccine was approved for use.
Among the four strains of HPV targeted by the vaccine, cases declined 88% among females age 14 to 19 and by 81% among women age 20 to 24 between 2003 and 2018.
"These data show increasing impact of HPV vaccination in the United States," the agency researchers wrote.
"HPV vaccination is a critical prevention tool against HPV infection, [anal and] genital warts, and HPV-attributable pre-cancers and cancers," they said.