China's top drug regulator has expanded the use of an imported vaccine against nine strains of the cancer-causing human papillomavirus to girls as young as nine and adults up to age 45.

While hailing the decision as part of China's endeavor to accelerate elimination of cervical cancer, experts said that given the tight supply of the 9-valent vaccine and increasing evidence of the efficacy of homegrown vaccines, it is wise to receive any approved HPV vaccines available.

The National Medical Products Administration first granted authorization to Gardasil 9, a 9-valent HPV vaccine created by global pharmaceutical giant Merck, for use in females aged 16 to 26 in 2018. On Aug 30, the administration said that its use is now broadened to females aged 9 through 45.

Currently, three imported HPV vaccines and two domestic vaccines have been approved for use on the mainland. Gardasil 9 is the only one that can shield nine strains of HPV, while the others offer protection against either two or four strains.

Qiao Youlin, a professor at the School of Population Medicine and Public Health at the Peking Union Medical College, said that HPV vaccines work best among teenage girls and those who have not had a sexual encounter, but sexually active women can still benefit from getting vaccinated.

"Expanding the age group eligible for the 9-valent vaccine will offer more options for Chinese females of different ages to prevent HPV infection and protect their health, and advance China's action to accelerate the elimination of cervical cancer," he said in a news release published by Merck on Aug 30.

In China, nearly 110,000 women were diagnosed with cervical cancer last year, and 59,000 had died of the disease, said Zhao Fanghui, a professor at the National Cancer Center and Chinese Academy of Medical Sciences' Cancer Hospital, citing data from the Global Cancer Observatory, a cancer data platform associated with the World Health Organization.

"Official data also show that the incidence of cervical cancer in China is rising and the average age of patients is getting younger, which is highly concerning," she said.

Eliminating the disease would require consolidated efforts in boosting the vaccination rate, especially among those aged under 15, as well as promoting early screening and treatment. Due to limited supplies and low awareness, China is now lagging far behind some leading countries in terms of immunization coverage, according to Zhao.

However, the rising number of highly effective domestic vaccines available on the market is expected to ramp up the efforts.

Six homegrown 9-valent HPV vaccines have entered the third stage of clinical trials, according to information shared by Dong Shaozhong, a researcher at Walvax Biotechnology, during a forum held during the weekend. Doses that protect against even more strains are also under research.

Even though the highly-coveted 9-valent vaccine is not easily available at present, Zhao said unvaccinated groups should not hesitate to receive a dose that protects against two strains.

A new study published in the journal The Lancet Infectious Disease on Aug 26 shows that Cecolin, the first domestic vaccine that protects against two HPV strains, is 100 percent effective in protecting against genital lesions－a precancerous condition－and 97.3 percent effective against persistent infection.

Zhao, who is involved in the study, said the data shows that the domestic vaccine's efficacy is on par with its international alternatives.

Moreover, the two types of HPV that the vaccine is capable of protecting against cause about 84.5 percent of cervical squamous cancer cases－the most common form of cervical cancer－in China, higher than the global average of 70 percent.

"The follow-up study that tracks more than 7,300 women for about 5.5 years adds evidence to the long-term protection provided by the domestic vaccine," she said. "It can also inform the formulation of public health policies and boost public confidence in and acceptance of domestic vaccines," she said.

While the latest authorization for Gardasil 9 means that more well-off groups can access the vaccine, Zhao suggested the general public not hesitate to receive available vaccines as soon as possible.