The FACTS on the Safety and Effectiveness of HPV Vaccine

There are two types of HPV vaccines approved for use in Canada, Gardasil^® and Cervarix ^®. The Gardasil^® vaccine was approved in Canada in July 2006. The vaccine is effective in preventing the types of HPV that are responsible for 70 per cent of cervical cancer. It is approved for males and females aged 9 to 26. The Cervarix^® vaccine was approved for use in Canada in February 2010 for females aged 10 to 25, and is effective in preventing the same types of HPV responsible for 70 per cent of cervical cancer. HPV is one of the most common sexually transmitted infections in Canada, and the majority of cervical cancers are caused by this infection. Despite the effectiveness of HPV vaccination, vaccinated females must continue to have regular cervical cancer screening.

In February 2007, based on sound scientific consideration, the National Advisory Committee on Immunization (NACI) issued recommendations for the use of Gardasil^® for females aged 9 to 26 (http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/07vol33/acs-02/index-eng.php). NACI is currently reviewing the evidence and considering recommendations related to the recent approval of Gardasil^® for use in males as well as the recent approval of Cervarix^®

All province and territories in Canada have implemented publicly funded HPV vaccine programs with a goal of reducing the risk that women will develop cervical cancer.

The information below answers some of the questions that have been raised about the safety and effectiveness of the HPV vaccines, as well as the need for an HPV immunization program. This information is based on current HPV immunization recommendations, and will be updated as necessary following the review of existing recommendations to consider the approval of Cervarix^® and the expanded approval of Garadasil^®.

Questions

• Who should receive the HPV vaccines?
• How many adverse events following HPV vaccination have been reported in Canada?
  
• How are vaccines monitored for safety in Canada?
  
• Why is a vaccine for a Sexually Transmitted Infection (STI) being given to girls as young as nine?
  
• What evidence is there that the HPV vaccines will provide long-lasting immunity?
  
• Is cervical cancer screening still necessary fro women who have been vaccinated?
  
• If cervical cancer screening programs are successful in Canada, is an expensive vaccine really needed?
  
• Some critics have argued that the HPV vaccines do not offer total protection against cervical cancer, and that other cancer causing types of HPV may become more prevalent. Is this the case?
  
• Have the costs and benefits of a mass HPV immunization program been fully assessed?

Answers

Who should receive HPV vaccines?

In February 2007, the National Advisory Committee on Immunization (NACI) issued recommendations for the use of Gardasil^® for females aged 9 to 26 (http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/07vol33/acs-02/index-eng.php). NACI is currently reviewing the evidence and considering recommendations related to the recent approval of Gardasil^® for use in males as well as the recent approval of Cervarix^®.

Gardasil^® is recommended for females between 9 and 26 years of age. The vaccine is thought to be most effective before the onset of sexual activity; however, females between the ages of 9 and 26 years can still receive the vaccine even if they have already been sexually active. Women who are already sexually active may be infected with an HPV type contained in the vaccine, but they can still benefit from protection against the other HPV types the vaccine protects against.

Females who have had previous Pap abnormalities, including cervical cancer, or have had genital warts or known HPV infection would still benefit from HPV immunization. These women may not have had infection with the HPV types included in the vaccine and are very unlikely to have been infected with all four HPV types contained therein. It is therefore recommended that these women receive the vaccine. However, they should be advised that there is no data to suggest that the vaccine will have any therapeutic effect on existing cervical lesions.

While Gardasil^® has been shown to be highly effective against cancer precursors caused by HPV-16 and 18; these two HR types of HPV are responsible for about 70 per cent of cervical cancer. Women who have been vaccinated will still be susceptible to other HR HPV types. Even if those types are less prevalent than HPV-16 or 18, these women should still expect to take part in the currently recommended cervical cancer screening programs.

Women who were already sexually active before receiving vaccine may have already been infected with HPV-16 or 18; therefore any sexually active woman should continue to take part in the routine cervical cancer screening program.

How many adverse events following HPV immunization have been reported in Canada?

As of September 30, 2009, PHAC has received 603 reports of adverse events following Gardasil^® HPV immunization. The majority of these adverse events were not serious adverse events. A serious adverse event is defined as a life-threatening illness or an adverse event that results in hospitalization, prolongation of an existing hospitalization, permanent disability or death.

The majority of the adverse events reported following HPV vaccine have been minor, such as injection site reactions. This is consistent with the results reported by clinical trials conducted prior to the approval of the vaccine and can be expected with the administration of any vaccine.

Twenty-two hospitalizations and one death following HPV immunization have been reported to date in Canada. None of the adverse events has indicated that there are any concerning trends or patterns linked to the HPV vaccine. An investigation of the death is ongoing; however, to date, results show that there is no evidence to suggest that the vaccine was the cause of death. PHAC continues to conduct ongoing vaccine surveillance to ensure that any emerging issues can be addressed as quickly and efficiently as possible.

How are vaccines monitored for safety in Canada?

The Public Health Agency of Canada coordinates and supports the Canadian Adverse Events Following Immunization Surveillance System (CAEFISS), which collects reports from health care providers on adverse events following immunization.

Canada also has an active surveillance system called IMPACT (Immunization Monitoring Program ACTive) that is based out of 12 paediatric hospitals across Canada. An expert scientific committee assesses the reports and determines whether or not the vaccine was likely to have caused the reaction.

Why is a vaccine for a Sexually Transmitted Infection (STI) being given to girls as young as nine?

After review of scientific and epidemiological data, NACI recommended vaccinating young women before they become sexually active in order to maximize protection against infection. PHAC supports these recommendations because immunization programs targeting girls before they become sexually active will result in a greater chance of providing protection prior to exposure to HPV. In clinical trials, the HPV vaccine was demonstrated to be safe and resulted in very high antibody levels when given to younger girls.

What evidence is there that the HPV vaccines will provide long-lasting immunity?

In clinical trials for Gardasil^®, pelvic examinations were conducted on women aged 15-26 and clinical specimens were taken in order to assess the effectiveness of the vaccine. Over the course of the five year study, the vaccine was shown to prevent the precursors to cervical cancer.

However, efficacy studies are not conducted in girls aged 9-13 because most are not sexually active so will have not acquired HPV. Pelvic examination is not done in this age group; therefore, “bridging” studies are undertaken which compare the antibody responses in younger females to those of older females who have undergone pelvic examinations to evaluate the vaccine’s efficacy. These clinical trials showed an excellent antibody response in the younger girls.

Of the girls aged 9-26 years involved in the clinical trials, more than 99 per cent produced antibodies for the HPV types included in the vaccine, and the trials showed that younger females (9-15 years) generate a very good immune response. This age group has not shown an elevated rate of side effects when compared to older age groups.

Is cervical cancer screening still necessary for women who have been vaccinated?

Yes. Gardasil^® and Cervarix^® do not prevent infection from all the HPV types that cause cervical cancer. However, both are effective in preventing the two types (type 16 and type 18), which cause 70 per cent of cervical cancers in Canada.

Given that there are other HPV types that can cause cervical cancer, it is very important for women to continue with cervical screening and practice safe sex as part of a comprehensive cervical cancer prevention strategy.

If cervical cancer screening programs are successful in Canada, is an expensive vaccine really needed?

Cervical screening has been successful in the reduction of cervical cancer deaths in Canada and should continue to form part of a comprehensive cervical cancer prevention strategy. It is a serious disease that affects hundreds of Canadian women each year.

Immunization can prevent some but not all of HPV infections. However, it offers significant advantages over the treatment of pre-cancerous and cancerous lesions once they have developed as immunization will reduce the number of procedures that women have to undergo and the associated pain and anguish of dealing with the diagnosis and treatment. When implemented in a school based program, immunization is likely to reach some of the populations who may have lower cervical cancer screening rates or poor follow up.

Some critics have argued that the HPV vaccinesdo not offer total protection against cervical cancer and that other cancer causing types of HPV may become more prevalent. Is this the case?

While it is important to collect data on changes in cervical cancer-causing HPV types over time, this should not discourage the implementation of an effective vaccine program that can benefit women now.

Gardasil^® and Cervarix^® do not prevent infection from all the HPV types that cause cervical cancer.

However, they are effective in preventing the two types (type 16 and type 18), which cause 70 per cent of cervical cancers in Canada.

Given that there are other HPV types that can cause cervical cancer, it is very important for women to continue with cervical screening and practice safe sex as part of a comprehensive cervical cancer prevention strategy.

Have the costs and benefits of a mass HPV immunization program been fully assessed?

Initially, the investment of the HPV vaccine appears costly. However, information needs to be collected to assess how the health care system, cervical screening and follow-up programs will be impacted by the introduction of the vaccine.

In the long term, the burden of disease on the health care system will decline with the reduction of HPV-related diseases, including genital warts, and cervical, vaginal and vulvar cancers and their pre-cursors.

This will mean less health care visits and reduced costs to the health care system, as well as less pain and suffering among the women in Canada who would have suffered from this form of cancer.

HPV immunization through school-based programs allows the provinces and territories to minimize the cost by immunizing students at the same time they receive other vaccines.