The FACTS on the Safety and Effectiveness of HPV Vaccine

The Gardasil® vaccine was approved in Canada in July 2006.  The vaccine is effective in preventing the strains of human papillomavirus that are 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.

The Chief Public Health Officer of the Public Health Agency of Canada (PHAC) reviewed these recommendations and strongly supports this vaccine.

The goal of the vaccination program is to reduce the risk that women will develop cervical cancer. Several provinces have announced plans to launch publicly-funded vaccine programs in the fall of 2007, and others intend to introduce programs next year.

The information below answers some of the questions that have been raised about the safety and effectiveness of the vaccine, as well as the need for an HPV immunization program.

Questions

• Is the HPV vaccine safe?
• What are the commonly found side effects to the vaccine?
• Who should receive the vaccine?
• Have there been reports of serious adverse events following HPV immunization?
• How are vaccines monitored for safety in Canada?
• Why do we need to immunize girls as young as nine?
• What evidence is there that the HPV vaccine is effective in young girls in view of the fact that the vaccine has not been thoroughly studied in nine-to-15 year olds?
• With studies on the vaccine limited to five years, what evidence is there the vaccine will be effective over the long term?
• Is it possible two rather than three doses of the vaccine would provide adequate protection?
• Is cervical cancer screening still necessary for 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 Gardasil®   does not offer total protection against cervical cancer, and that other cancer causing strains 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

Is the HPV vaccine safe?

Yes, the vaccine is safe. Health Canada approves vaccines for use in Canada following rigorous scientific review and testing for their quality, safety and effectiveness.  Once a vaccine is in use, Health Canada and the Public Health Agency of Canada conduct ongoing monitoring to ensure its continued safety and efficacy.

In June 2007, the World Health Organization's Advisory Committee on Vaccine Safety reviewed all available data that addressed the safety of HPV vaccines and expressed no concerns regarding the vaccines' safety to date.

 What are the commonly found side effects to the vaccine?

Like all vaccines, Gardasil® has some side effects including injection site reactions (pain, redness, swelling), which are consistent with results reported in clinical trials conducted on the vaccine. As well, there have been reports of fainting episodes following vaccination which are not uncommon when vaccines, such as the Hepatitis B vaccine, are administered to adolescents.

Who should receive the vaccine?

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 Gardasil™. 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.

Have there been reports of serious adverse events following HPV immunization?

As of Nov 2, 2007, PHAC received a total of 127 reports of adverse events, none of which were of death or Guillain Barré syndrome (GBS).

These reports are mostly of minor adverse events, including injection site reactions, which are 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.

Three hospitalizations following HPV immunization have been reported to date in Canada, none which were likely related to the vaccine.

In the U.S., millions of doses of the vaccine have been distributed and the number of serious adverse events has been very rare. For more information about adverse events following HPV immunization in the U.S., please visit the Vaccine Adverse Events Reporting System (VAERS) website.

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, which collects reports from health care providers on adverse events following immunization.

Canada also has an active surveillance system that is based out of 12 paediatric hospitals across Canada, called IMPACT (Immunization Monitoring Program ACTive). An expert scientific committee assesses the reports and determines whether or not the vaccine was likely to have caused the reaction.
 
Why do we need to immunize 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 vaccine is effective in young girls in view of the fact that the vaccine has not been thoroughly studied in nine-to-15 year olds?

In clinical trials, 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 not have acquired HPV and pelvic examination is not done in this age group; therefore, “bridging” studies are undertaken. These 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% produced antibodies for the HPV types included in the vaccine, and 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.

With studies on the vaccine limited to five years, what evidence is there the vaccine will be effective over the long term?

Clinical trials have shown that the vaccine is safe and effective for at least five years.

It is not known at this time whether a booster dose will be needed. Continued surveillance and research into how long the vaccine will be effective and whether or not booster shots will be needed is underway. The good immune response seen in vaccine recipients during clinical trials indicates that vaccine protection is likely to last for many years.

When a new vaccine is approved for use, it is not unusual for there to be a number of unanswered questions about the duration of protection and the vaccination schedule.

Successful vaccination programs are routinely implemented without long-term efficacy data at the start but data is collected along the way to determine if protection lasts and if a booster is needed. For example, when the meningococcal vaccine was introduced there was no data on the duration of protection and we may have to consider booster doses in the future

Is it possible two rather than three doses of the vaccine would provide adequate protection?

NACI's recommendations are based on current evidence. Further study on the effectiveness of a two-dose HPV vaccine schedule is required and as data from on-going research becomes available, recommendations will be updated accordingly.

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

Yes. Gardasil® does not prevent infection from all the HPV strains that cause cervical cancer. However, it is 100 per cent effective in preventing the 2 strains (strain 16 and strain 18), which cause 70 per cent of cervical cancers in Canada.

Given that there are other HPV strains 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.

Cervical cancer is a serious disease that affects hundreds of Canadian women each year. As a result of screening for cervical cancer with the Pap test, the incidence and mortality of cervical cancer have declined over the past 30 years. Still, it is estimated that about 1,350 Canadian women will be diagnosed with cervical cancer this year and that there will be nearly 400 deaths.

Immunization can prevent HPV infection and therefore offers significant advantages over the treatment of pre-cancerous and cancerous lesions once they have developed. It 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. 

The major burden of the disease in Canada is not only the number of cancers; it is the number of women with abnormal test results. While the vaccine won't eliminate the disease, it will reduce the emotional costs of a pre-cancer diagnosis and the financial costs of early treatment.

Some critics have argued that Gardasil®   does not offer total protection against cervical cancer, and that other cancer causing strains of HPV may become more prevalent. Is this the case?

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

Gardasil® does not prevent infection from all the HPV strains that cause cervical cancer.

However, it is 100 per cent effective in preventing the 2 strains (strain 16 and strain 18), which cause 70 per cent of cervical cancers in Canada.

Given that there are other HPV strains 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.