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<p>The human papillomavirus (HPV) vaccines have demonstrated very high vaccine efficacy
against the vaccine types and related disease in clinical trials when administered
to HPV-naïve women (i.e. women with no current or previous vaccine-type HPV infection).
However, results from these trials also demonstrated that HPV vaccination of women
with a current vaccine-type HPV infection had little or no effect on clearance of
the existing infection. There is also some evidence of a slightly reduced vaccine
efficacy against pre-cancerous abnormalities among young women currently not infected
with HPV but with serological evidence of a previous exposure.</p><p> </p><p>Public
Health England has conducted surveillance to monitor the prevalence of type-specific
genital HPV infections in 16-24 year old sexually active women in England who would
have been eligible to receive the HPV vaccine. The latest data, including specimens
collected to the end of 2016, demonstrated a vaccine effectiveness of 82.0% against
infections with HPV16/18 among women vaccinated at age 15 years or younger. The vaccine
effectiveness in women who would have been vaccinated at age 16 to 18 years old was
48.7%. This suggests that the vaccine works best when given to young girls before
they are exposed to HPV. However it also shows that older girls still benefit from
vaccination.</p>
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