Drug Criteria & Outcomes
Test Your Vaccine Knowledge: Gardasil®
Part I of a Series on Vaccines
By Meagan Widener, PharmD Candidate Harrison School of Pharmacy, Auburn University
Immunization awareness plays an important role in patient care; in fact, most adults are unaware that immunizations are not just for kids anymore. Therefore, it is the responsibility of health care providers to be knowledgeable about pertinent vaccines for their patient population.
The vaccines available today afford benefit to a wide range of ages: infants, adolescents, adults, and the elderly. Many of the vaccines provide a proactive response to the conditions that were treated only retrospectively just a few years ago. A new vaccine currently available for the adolescent and young adult female population, Gardasil®, gained FDA licensure in June 2006 to combat human papillomavirus (HPV)-induced cervical cancer and genital warts.1
Studies indicate that immunization rates of adults are extremely low. The CDC's National Immunization Survey, performed in 2007, showed that only 9.9% of women ages 18-26 had received Gardasil.2
Because these unacceptably low rates are primarily due to unawareness of both the vaccine and the threat of the potential infection, it is up to all health care providers to educate patients about these issues. If responsibility, awareness, and action are taken now, unnecessary cases of preventable illness can begin to decline.
The purpose of this article is to inform and update health care professionals about Gardasil and to improve screening for potential candidates at each encounter. A case report is presented next with background information about the disease, then the vaccine and appropriate follow-up are discussed.
Case
SJ is a 26-year-old female who is a new patient that has a family history of cervical cancer, breast cancer, and hypertension. She is interested in the new Gardasil vaccine she has heard advertised on television and wondered that since she is sexually active if there is a need to receive the vaccine. She also would like to know how much the series costs. Is this patient a candidate for Gardasil?
Background
HPV is the most common sexually transmitted disease in the United States. More than 20 million cases are currently documented, the number continues to grow as 6.2 million new cases are discovered each year. There are more than 200 types of HPV. Infections with these serotypes can result in genital warts and many types of cancer including vaginal, vulvar, penile, anal, and cervical cancers. Typically, exposure occurs within the first few years of sexual activity. By age 50, estimated 80% of those sexually active will have at least one HPV serotype infection. In many cases, HPV infections clear spontaneously and are asymptomatic. However, about 15 strains are considered high oncogenic risk types, including types 16 and 18, and are more likely to persevere for years. These two strains are especially contributory to cervical cancer: Studies show HPV serotype 16 is causative of 50.5% and serotype 18 is responsible for 13.1% of all cases of cervical cancer. Patients should be educated on prevention and screening methods. These include safe sexual practices, vaccination against HPV, and regular HPV screenings.3,4
Vaccine mechanism
Gardasil is a non-infectious, recombinant vaccine composed of four virus-like proteins (VLPs) from the major capsid protein (L1 protein) for HPV strains 6, 11, 16, and 18. The L1 VLPs exert efficacy by mediating initiation of the immune system's humoral response. Strains 16 and 18 are 70% likely to cause cervical cancer and strains 6 and 11 are 90% likely to cause genital warts.3,5
Candidates for the vaccine
Gardasil is not a live vaccine, which prevents it from posing risks to those who are immunocompromised, unlike live vaccines which are contraindicated in this population. Currently, the vaccine is only approved for women ages 9-26. Emphasis is placed on early vaccination at ages 11-12, not only to ensure protection prior to sexual activity, but also to increase efficacy of the vaccine.4,5 Studies show that titers are higher in females ages 9-15 years than ages 16-26 years. The patient should be informed that even if she is already sexually active, benefits remain in receiving the vaccine. If a patient has been exposed to certain strains of HPV, it is unlikely that all strains have been encountered.3,4
Who should not receive the vaccine
Those with hypersensitivity to the vaccine components, including those with S. cerevisea yeast hypersensitivity, or who develop hypersensitivity during the series should not receive Gardasil. The vaccine should not be administered to pregnant patients or to male patients, although the use in males is currently being investigated. Children younger than 9 years and adults older than 26 years should not be given the vaccine. Defer use of the vaccine if current febrile illness is present, but low-grade fevers and mild upper respiratory tract infections should not be considered contraindications. As with other intramuscularly injected vaccines, those with risk of increased bleeding should not receive Gardasil unless benefits exceed risks in these patients. Those seeking treatment of cervical cancer or genital warts infection should be informed that this vaccine is only for prevention.3
Administration
Gardasil should be administered via IM injection in either the deltoid or high anterolateral area in three separate 0.5 mL doses given at 0, 2, and 6 months. It is imperative to stress the importance of receiving the entire series, as titers have proved to be higher after the third dose than with the previous doses.3 If doses are not given within the allotted time periods the series should be continued, not restarted.4 Prior to immunization, the patient or guardian should receive the Vaccine Information Statements, a requirement by the National Childhood Vaccine Injury Act of 1986. Since the administration of hepatatis B vaccine uses the same scheduled dosing periods, coadministration with Gardasil on the same day was evaluated. No reports of adverse effects were reported, but administration at different injection sites was suggested.3
Efficacy
Reports show that more than 99% of all vaccinated patients develop HPV antibodies after vaccination, and the vaccine is 95-100% efficacious in preventing cervical intraepithelial neoplasia and adenocarcinoma in situ. In combating genital wart serotypes included in the vaccine, Gardasil has shown 99% efficacy.3 The vaccine has proven to be effective in preventing both conditions for up to 5 years, but further studies should be completed to determine if a subsequent booster is needed.5
Adverse reactions
Mild-to-moderate injection site pain, swelling, and erythema have been reported.3,5 Post-marketing reports show that syncope has occurred in some patients, especially the younger population; therefore, observation should occur for at least 15 minutes following the vaccine. Reports have also indicated that there could be a risk of anaphylaxis, lymphadenopathy, headache, dizziness, and Guillain-Barré syndrome. Any events of this nature should be reported using the Vaccine Adverse Event Reporting System (VAERS).3
Patient cost
The three-dose series costs the patient approximately $360 and may pose a complication in meeting desired immunization rates. While many insurance companies cover the vaccine to some degree (age and compensation vary with each company), the vaccine is still virtually inaccessible to those who are uninsured. Sadly, more than one in 10 girls ages 9-18 and more than one in four women ages 19-26 are uninsured and might not be able to afford the vaccine. Fortunately, several programs such as Vaccines for Children (VFC), the Immunization Grant Program, Medicaid, the State Children's Health Insurance Program, and other various state-specific programs lend opportunities to receive the vaccine for women younger than 21 years of age. Merck has also established a vaccine assistance program for women ages 19-26 who meet certain criteria and are uninsured.5
Further research
Since March 19, 2008, the FDA began considering approval of a study planned by Merck that involves the use of Gardasil in women ages 27-45. The final decision on this matter is projected to be announced this summer.1 Another vaccine against HPV, Cervarix®, developed by GlaxoSmithKline is currently under FDA review. This vaccine targets only strains 16 and 18.1,4 Merck is also currently studying the efficacy of the three-dose series HPV vaccine in men ages 16-23 with hopes to have the indication for this population by next year. Anal cancers in gay men are becoming as predominant as cervical cancer in women, therefore, this indication is greatly needed.6
Patient follow-up
The patient, SJ, is indeed a candidate for Gardasil. She is not currently pregnant, within the recommended age range, and is sexually active. The patient should be informed that the vaccine series will cost about $360 and that Merck's vaccine assistance program might cover the cost of her vaccine if she meets certain eligibility criteria.
[Addendum: Gardasil Vaccine Safety Update. Recently, the news media has raised questions concerning more than 8,000 reports of a variety of adverse effects occurring in association with the administration of the Gardasil vaccine. These effects include Guillain-Barre Syndrome (GBS), and even death. Most of these reports (94%) were not serious and are known to occur with administration of various vaccines, including Gardasil (i.e., syncope, dizziness, nausea, vomiting, and hypersensitivity). The Centers for Disease Control and Prevention (CDC) has evaluated the available data and concluded that currently there is not enough evidence to suggest a link with these deaths and Gardasil administration. Additionally, they were unable to establish a link between Gardasil administration and GBS, as information does not currently demonstrate a higher rate of GBS occurrence post-vaccination vs. rates that would normally occur in the targeted age group population. Both the CDC and FDA continue to emphasize that the Gardasil vaccine is safe, effective, and important. It will be important in the future to monitor the safety of Gardasil as well as other vaccines. Practitioners are encouraged to report adverse events associated with vaccines through the Vaccine Adverse Event Reporting System (VAERS), P.O. Box 1100, Rockville, MD 20849-1100; telephone (800) 822-7967; e-mail [email protected], or visit the web site at http://vaers.hhs.gov/.]
References
- Red Book® Online Table – Status of Licensure and Recommendations for New Vaccines. Red Book Online by American Academy of Pediatrics. Available at: http://aapredbook.aappublications.org. Updated May 5, 2008. Accessed June 6, 2008.
- Euler GL, Lu P, Singleton JA. Vaccination coverage among U.S. adults National Immunization Survey — Adult 2007. Available at: www.cdc.gov/vaccines. Revised March 26, 2008. Accessed June 6, 2008.
- Gardasil® [package insert]. Whitehouse Station, NJ: Merck & Co., Inc; December 2007.
- Zimmerman RK, Middleton DB, Kimmel SR. Vaccines across the life span. J Fam Pract 2007;56:S1-S33.
- Women's Health Policy Facts. HPV Vaccine: Implementation and Financing Policy in the U.S. The Henry J. Kaiser Family Foundation. Available at: www.kff.org/womenshealth/upload/7602_02.pdf. Published February 2008. Accessed June 12, 2008.
- Burkholder A. Young men and the HPV vaccine. Available at: www.cnn.com/HEALTH/blogs. Published March 10, 2008. Accessed June 13, 2008.
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