Using GlaxoSmithKline's Cervarix vaccine to protect girls against the HPV virus that causes cervical cancer is so effective that health authorities could reduce the need for later cervical screening, scientists said on Wednesday.
Researchers from Finland and the United States who published two studies in The Lancet Oncology journal found Cervarix "offers excellent protection" against two key strains of the human papillomavirus (HPV), particularly when given to young adolescent girls before they become sexually active.
The studies also found the vaccine partially protects against several other cancer-causing HPV types that it is not specifically designed to target, giving protection against a group of strains that together cause about 85 percent of cervical cancer worldwide.
"Provided that organised vaccination programs achieve high coverage in early adolescents before sexual debut, HPV vaccination has the potential to substantially reduce the incidence of cervical cancer, probably allowing the modification of screening programs," said Matti Lehtinen from the University of Tampere in Finland, who worked on the studies.
He said that as a result of the findings health experts in Finland, one of the first countries to introduce nationwide HPV vaccination campaigns in 2007, should consider cutting cervical screening programs down to just a once-in-a-lifetime test at around the age of 25 to 30 to check the vaccine has been fully effective.
"You should not have two measures on top of each other if one is already efficient enough," he said in a telephone interview. "This could certainly mean lots of savings in terms of costs of screening."
GSK's two-strain vaccine targets HPV types 16 and 18 that are responsible for about 70 percent of cervical cancers. Rival drugmaker Merck also makes an HPV vaccine called Gardasil which protects against 16, 18 and two other strains of the virus.
Cancer of the cervix is the second most common cancer in women worldwide, with about 500,000 new cases and 250,000 deaths each year, according to the World Health Organization.
Virtually all cases are linked to genital infection with HPV, the most common viral infection of the reproductive tract.
Several developed nations have in recent years introduced nationwide HPV vaccination programs for girls and young women.
In the United States, for example, the Centers for Disease Control and Prevention currently recommends girls and women aged between 11 and 26 should get either Cervarix or Gardasil.
Lehtinen said these vaccinations could eventually cut the need for nationwide cervical smear screens that are usually done every few years in women from around the age of 25 onwards.
The two Lancet Oncology studies both looked at Cervarix.
The first, which included almost 20,000 healthy women aged between 15 and 25 from 14 countries across Asia, Europe, Latin America, and North America, found the shot gave high rates of protection against high-grade cervical precancers, early development of a condition called adenocarcinoma, and 12 other cancer-causing HPV types.
In a second study the vaccine showed increased cross-protection against other cancer-causing HPV types 31, 33, 45, and 51 in different groups of women.
"Our results show that cross-protective efficacy might provide substantial additional protection against cervical cancer," said Cosette Wheeler from the University of New Mexico in the United States, who co-led the second study.
In a commentary about the findings published in the same journal, Mark Schiffman and Sholom Wacholder from the U.S. National Cancer Institute said that increasing coverage, particularly of as yet sexually-naive young girls, "is now the most important public-health issue in HPV vaccination efforts."