|
 "The magnitude of the effect is greater than expected," study author
Dr. Tim Palmer from the University of Edinburgh told Reuters Health
by email.
Receiving three doses of the vaccine at the recommended ages of 12
to 13 was associated with "a profound reduction of cervical disease
seven years later," he and his colleagues report in The BMJ.
One of the most common sexually transmitted diseases, HPV doesn't
cause symptoms and usually goes away on its own. But the virus can
cause cancer of the cervix, the fourth most common cancer in women,
as well as cancers of the throat and penis.
Palmer's team studied 138,692 women, about half of whom had been
fully vaccinated against HPV either at ages 12-13, or later in their
teens. At age 20, the women all had tests to look for abnormal cells
on the cervix - called cervical intraepithelial neoplasia, or CIN -
that can lead to cancer.
Rates of CIN were low overall. But compared with unvaccinated women,
vaccinated women had an 89 percent lower rate of CIN grade 3 or
worse (0.59 percent in unvaccinated women versus 0.06 percent in the
vaccinated group), an 88 percent lower rate of CIN grade 2 or worse
(1.44 percent versus 0.17 percent), and a 79 percent lower rate of
CIN grade 1 (0.69 percent versus 0.15 percent).
Grades 2 and 3 are usually treated with surgery.
Girls who were vaccinated at ages 12-13 got a greater benefit: the
vaccine was 86 percent effective for them, and 51 percent effective
when given at age 17.
"The findings are dramatic and document a considerable reduction in
high-grade cervical disease over time," Julia Brotherton, medical
director at VCS Foundation in East Melbourne, Australia, writes in
an editorial published with the study.
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In the U.S., many girls and boys don't receive the vaccine at least
in part because their parents may question whether it's necessary to
protect them against a sexually transmitted disease at an age when
they think children shouldn't be having sex, previous studies have
found.
Scotland, which has an organized national cervical screening
program, introduced a national immunization program against HPV in
2008, targeting girls aged 12 and 13, followed by a three-year
catch-up program up to age 18.
The study also revealed a decreasing rate of disease in unvaccinated
women. "This is called herd protection and is a function of the high
uptake of vaccine in Scotland," Palmer explained. Unvaccinated women
are being protected because the spread of HPV between men and women
has been interrupted because there are not enough susceptible women,
he said.
There were an estimated 570,000 new cervical cancer cases globally
in 2018, representing 6.6 percent of all female cancers, according
to the World Health Organization, with about 90 percent of deaths
from cervical cancer occurring in low- and middle-income countries.
These countries, however, do not have the resources to support
organized screening, the authors write, highlighting the importance
of developing vaccines against the most important cancer-causing HPV
strains.
In February, the WHO and cancer experts called the HPV vaccine a
"critical" health tool and said access to it should be scaled up as
swiftly as possible, especially in poorer countries.
SOURCE: https://bit.ly/2WWlBLQ and http://bit.ly/2KEmDuH The BMJ,
online April 3, 2019.
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