ATLANTA (CNNMoney.com) - Vital protection against cervical cancer could soon be made available, not just from Merck but also from GlaxoSmithKline, providing life-saving potential for women while feeding a competitive atmosphere for the drug giants.

The expected FDA approval for Merck's experimental cervical cancer vaccine Gardasil is just days away. Merck (Research) could soon find itself marketing this potential blockbuster with no competition, at least for a while, even as it rebuilds its Vioxx-tainted reputation with a vaccine that has drawn praise as a potential boon to public health.

The Food and Drug Administration is expected to announce its Gardasil decision on Thursday, and few doubt the vaccine will get the thumbs up, especially since approval was unanimously recommended by FDA advisors. The vaccine has drawn strong annual sales projections from analysts, from $1.6 billion to as much as $4 billion.

But Merck's rival-free landscape might not last past 2006. GlaxoSmithKline (Research) could soon follow with its own vaccine, Cervarix, which is in the last stages of study.

"We will certainly have it on the market by 2007," said Brian Lortie of GlaxoSmithKline, vice president of worldwide operations for Cervarix, who expects to file an FDA application for the vaccine later this year.

Lortie downplayed any notion of the two vaccines as competitors, and applauded his rival's product as a benefit to women's health. "We'll be thrilled and excited to see Gardasil approved," he said.

A GlaxoSmithKline-funded late-stage study was announced Monday for Cervarix at the annual conference of the American Society of Clinical Oncology.

The results of this study showed that 100 percent of women aged 26 to 55 had immune responses against strains of the human papillomavirus, the sexually transmitted virus that causes most cases of cervical cancer. An immune response is used by researchers to determine whether a vaccine might protect women against viral infection.

This Cervarix study is distinct from Gardasil studies because it was conducted in older women, showing that they could benefit from inoculation against HPV.

"Women of all ages can be exposed to HPV infection," said James Tursi of GlaxoSmithKline, medical director for HPV research. "If they're sexually active, they can be exposed, not just women who are 15 and 16."

Previously announced studies for both vaccines tended to focus on younger girls, some of them prepubescent, to guard them against the sexually-transmitted virus later in life.

This sparked concerns among conservative groups about sexual morality, but this controversy has largely died down, and Merck convinced some religious groups to come out in favor of the vaccine.

A separate, earlier-stage study, released in April, showed that Cervarix prevented pre-cancerous lesions in girls and women aged 15 to 25 over the four-and-a-half year duration of the study and they maintained strong immunity during that time. Researchers see this as an important indication that the vaccine could prevent cervical cancer.

"By preventing these pre-cancerous lesions, we will prevent the cervical cancer that would have resulted," said Tursi.

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