|
 HPV vaccination is intended to prevent cervical cancer and abnormal
cells that can lead to cancer, but how well it’s working among North
American women remains unclear.
“Both HPV vaccination and cervical cancer screening are important to
further reduce the incidence, morbidity, and mortality of cervical
cancer,” senior study author Dr. Huiming Yang from Alberta Health
Services in Calgary told Reuters Health by email.
The province of Alberta implemented a school-based HPV vaccination
program for girls in 2008 and expanded it to include boys in 2014.
The HPV vaccination program provides three doses of the vaccine over
a six-month period.
Yang and colleagues studied the impact on Pap test results eight
years into this program.
The researchers analyzed data on 10,204 women, 56 percent of whom
were unvaccinated and the rest had received at least one dose of HPV
vaccine before having cervical cancer screening.
Overall, 14.5 percent of women had abnormal Pap tests and 85.5
percent had normal tests. Most abnormal tests, nearly 94 percent,
were low-grade abnormalities, but the rest were the high-grade
abnormalities that could progress to cervical cancer.
Less than 12 percent of women who had received at least three doses
of the vaccine had abnormal Pap results, whereas 16 percent of
unvaccinated women had abnormal tests. This translates into a 28
percent risk reduction with full HPV vaccination.
The difference was even greater – a 50 percent reduction in risk –
when only high-grade abnormalities were included, according to the
results published in CMAJ.
Surprisingly, incomplete HPV vaccination with two or fewer doses of
the vaccine was not associated with a lower risk of having an
abnormal Pap test.
"Our study shows that three doses HPV vaccination is very effective
in reducing cervical cell abnormalities, particularly for high-grade
lesions, but two does not appear to offer similar protection,” Dr.
Yang concluded. “It is important to complete all scheduled doses of
vaccine.”
[to top of second column] |
"I found it interesting that young women in this study that received
two doses of the quadrivalent vaccine had similar odds of having an
abnormal Pap as those who had 0 doses,” said Dr. Jacqueline M. Hirth
from the University of Texas Medical Branch, Galveston, who has also
studied the effect of HPV vaccination on cervical cancer screening
among young women.
That result should be interpreted with caution, she told Reuters
Health by email, since many of the young women in this sample were
under 21 years of age and may not have been receiving routine Pap
screenings.
“They may have actually gone to their providers for abnormal
bleeding or other symptoms, which may have prompted them to receive
Pap tests that would not have met the criteria for ‘routine’
screenings,” Hirth said.
HPV vaccination in combination with cervical cancer screening
according to guidelines is important for the prevention of cervical
cancer, Hirth said, because the HPV vaccine does not protect against
all high-risk HPV types.
She added that it's important for women to receive all three doses
of the HPV vaccine and to undergo cervical cancer screening
regardless of vaccination history in order to reduce their risk of
developing HPV-related cancers.
SOURCE: http://bit.ly/29ig8pw CMAJ, online July 4, 2016.
[© 2016 Thomson Reuters. All rights
reserved.] Copyright 2016 Reuters. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.
 |
