GlaxoSmithKline's Cervarix may have been the first HPV shot approved in mainland China, but Merck's Gardasil now has an opening to gain the lead.

Cervarix hasn't launched yet in the country, and as of Monday, Gardasil now has its own green light. Merck and its marketing partners have set hefty first-year sales expectations, setting up a race for share against the GSK shot.

Just like Cervarix, Gardasil won its go-ahead after a years-long approval slog at China's FDA. Merck started the application process in the country just a few months before it won its first approval worldwide—from the U.S. FDA—in June 2006.

To help launch in China, Merck struck an exclusive marketing deal with Zhifei Biological Products, a local vaccine-focused company, back in 2012. According to the company's disclosure (Chinese, PDF) Zhifei is contracted to buy 1.14 billion Chinese yuan ($166 million) worth of Gardasil from Merck for the first year after its official launch there. Another 1.48 billion yuan ($216 million) purchase is planned for the second year, and 1.85 billion yuan ($268 million) for the third.

The Gardasil arrangement is part of a larger tie-up between Zhifei and Merck that began in 2011. The two renewed their contract in April, continuing Zhifei’s marketing rights to pneumococcal vaccine Pneumovax and hepatitis A vaccine Vaqta.

Cervarix protects against two types of HPV (types 16 and 18). Citing "very low market demand," GSK pulled the vaccine off the U.S. market last October, just three months after its approval in China.

The emerging market could breathe new life into the vaccine for the British drugmaker; after all, cervical cancer cases have been noticeably increasing in China in recent years. New incidence in 2015 was estimated at around 99,000, according to a study sponsored by the Chinese government, published in CA: A Cancer Journal for Clinicians.

GSK has been in talks with the Chinese government to potentially get Cervarix listed on the country's National Immunization Program, Yingwei Zhang, GSK China's director for corporate communications and government affairs, told China business news Yicai (Chinese) in an interview after Cervarix was approved. Getting in the national program would be a big step toward a vaccine's (Cervarix and Gardasil included) success there, since it will be made accessible to a far larger population. 

Now that Gardasil has been approved in China, the full revival of Cervarix could be put in question, however. Although Cervarix protects against HPV strains that account for about 70% of cervical cancers, Gardasil offers additional protection against types 6 and 11, which can cause genital warts.

Nevertheless, at least for now, there's one thing that Cervarix could differentiate itself from Gardasil in China, and that's approved target age groups. CFDA approved Cervarix for immunization in women ages 9 to 25, but Gardasil's current approval is for females ages 20 to 45, different from its U.S. FDA's approval for those 9 through 26. Given that the primary target group in most of the countries recommending HPV vaccination is young adolescent girls aged 9 to around 14 (before they're sexually active), Cervarix could offer more potential. But it's likely that Gardasil will seek approval expansion.

In December 2014, Merck nabbed U.S. approval for an updated version, Gardasil 9, which covers five more HPV strains responsible for about 20% of cervical cancers. The Gardasil family reeled in $2.17 billion in 2016 sales for Merck, and life science commercial intelligence firm Evaluate's most recent estimate in April for Gardasil's 2022 sales was around $2.07 billion, slightly downward from its previous forecast but would still place the vaccine as the second-best-selling vaccine product around the world.

Editor's Note: The story has been updated to reflect that Gardasil's approved target age group in China is different from that of Cervarix's, plus Evaluate's most recent sales estimate for Gardasil.