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How was the HPV vaccine tested?

The initial clinical trials for the HPV vaccine involved more than 20,000 women aged 16 to 26 from 33 countries, including Australia.

The trials did not seek to prove that the vaccine prevents cervical cancer. This is because it would not have been ethical to allow cervical cancer to develop in the group who did not receive the vaccine in the trials (the placebo or control group).

However trials showed that the vaccine is almost 100% effective in preventing abnormalities in cells in the cervix caused by high-risk HPV types 16 and 18. These abnormalities are a proven pre-cursor to cervical cancer.

Further clinical trials involving more than 4,000 males aged 16 to 26 years from 18 countries showed the vaccine was 90% effective against HPV types 6, 11, 16 and 18 that cause genital warts and penile lesions, and 78% effective against HPV types 6, 11, 16 and 18 that cause anal lesions in men.

For ethical reasons, younger girls were not included in the trials as they would have been required to have regular Pap tests, which would have been inappropriate given their age.  Younger boys were also excluded from the trials.

Instead, studies compared the body's immune response to the vaccine between younger and older girls, and younger and older boys. It was determined those younger girls and boys who received the vaccine in these studies:

  1. Experienced no increased adverse reactions to the vaccine compared to older girls and boys.
  2. Created more antibodies in response to the vaccine than older girls and boys, meaning we can expect them to be better protected against HPV

Over 205 million doses of the Gardasil vaccine have been distributed worldwide as of 31 December 2015.

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Trials showed that the vaccine is almost 100% effective in preventing abnormalities in cells in the cervix caused by high-risk HPV types 16 and 18.

Design and partial content reproduced with the kind permission of the New Zealand Ministry of Health.

The HPV vaccine is a prescription medicine. Medicines have benefits and risks. After reading this website, talk to your doctor about the benefits and risks of this vaccine and to check eligibility.

Females who have had the HPV vaccine still need regular Cervical Screening Tests.