WASHINGTON (AP) — Efforts to develop the world’s
first vaccine to prevent cervical cancer took a key step forward
yesterday with test results suggesting that it can provide
long-lasting protection.

Four years after getting the vaccine, 94 percent of women were
protected from infection with the virus that causes most cervical
cancers and none had developed worrisome precancerous conditions, a
study showed.

“We’re thrilled about these results. The immune
responses seem to be really long-lasting,” said Eliav Barr,
who leads development of the vaccine for Merck & Co. The
company plans to seek U.S. Food and Drug Administration approval
next year for an expanded version of the vaccine that also could be
used to prevent genital warts in both women and men.

The new study was funded by Merck and led by University of
Washington researchers who presented results yesterday at a meeting
of the American Society for Microbiology.

“They showed clear effectiveness,” said Scott
Hammer, a Columbia University infectious disease expert who
reviewed the work but has no ties to Merck or the study.
“This is a very important issue for women’s health
around the world.”

If the vaccine makes it to market, it would be the second
developed to prevent cancer. The hepatitis B vaccine has
dramatically reduced the number of infections that progress to
liver cancer.

Cervical cancer strikes nearly half a million women worldwide
each year and kills about half. In the United States, about 15,000
women get it and about 5,000 die.

Virtually all cases are caused by infection with human papilloma
virus, or HPV, which is spread through sex. One strain, HPV-16,
accounts for about half of all cervical cancers.

A previous study showed that HPV-16 infections were completely
prevented in 768 women who had received the Merck vaccine 18 months
earlier. None developed precancerous conditions either.

The new study followed 755 of these women for four years after
vaccination. HPV-16 infections had taken hold in seven; none
developed precancers. In a comparison group of 750 women who
received dummy shots, infections took hold in 111 and precancers
formed in 12.

Even though protection had waned for a small number of women in
the study, the vaccine’s effectiveness was still very high,
said Douglas Lowy, a National Cancer Institute scientist who
invented the vaccine. The government gave rights to develop it to
two companies — Merck and GlaxoSmithKline — and
Merck’s work is a little farther along, Lowy said.

“Revaccination might be advisable at some point,”
but it will take more study to know whether that is necessary or
would improve effectiveness, he said.

Women in the study were ages 16 to 23 when they received the
vaccine, given in three doses over six months.

“Most people think it would be recommended for young
adolescents. The idea would be you would immunize people relatively
soon before they become sexually active,” because the germ is
spread through sex, Lowy said.

Meanwhile, Merck is in the final stages of testing an expanded
vaccine. Besides HPV-16, it contains strain 18, which causes
another 10 percent to 20 percent of cervical cancers, as well as
strains that cause genital warts in men and women, and penile and
anal cancers in men.

About 25,000 women and men have been enrolled in that study in
34 countries, and results are expected next year, Barr said.

Giving the vaccine to men would not only prevent disease in them
but also would prevent infections in their partners, said Steven
Projan, a drug development expert with Wyeth who helped review
research for the microbiology meeting. The vaccine also might
prevent women already infected with HPV from developing cancer, he
said.