Safety and Immunogenicity of Human Papillomavirus (HPV) Vaccine in Solid Organ Transplant Recipients.
Cervical cancer affects a significant proportion of the female population. In Canada, it is
estimated that there will be 1,350 new diagnoses of cervical cancer in 2007 and 390 deaths
. Human papillomavirus (HPV) is the causative agent in genital warts, cervical
intraepithelial neoplasia, and cervical cancer. In this study, the vaccine will also be
given to males, because males can develop anogenital warts and can transmit the virus to
their partners. HPV is a nonenveloped DNA virus containing early and late genes. Although
approximately 40 HPV types can infect the genital tract, only a few cause the majority of
disease. For example, cancer-causing HPV includes HPV 16 whereas benign tumours are caused
by HPV 6 .
HPV vaccine is a quadrivalent vaccine consisting of HPV types 6,11,16,18. Types 16 and 18
are implicated in the majority (~70%) of cervical cancers and at least half of CIN 2 and 3
lesions. Types 6 and 11 cause 90% of genital warts. The vaccine contains virus-like
particles (VLPs) of the L1 proteins of the four serotypes and is adjuvanted with aluminum
hydroxyphosphate sulphate. The vaccine does not contain live virions and cannot cause HPV
disease. It is administered by intramuscular injection in three doses at 0, 2 months, and 6
HPV vaccination is effective in the prevention of high grade cervical lesions and is now
recommended for all females aged 9-26 years by the Canadian National Advisory Committee on
Immunization (NACI) . Although the vaccine is licensed for females, males can also
develop anogenital warts and can transmit the virus to their partners. Immunogenicity
trials have shown similar response to vaccine in adolescent males compared to females .
In addition, if women have been infected with 1-3 out of the four serotypes, vaccination
appears to prevent cervical lesions from the remaining serotypes . Therefore, although
the vaccine is licensed for women ≤ 26 years old, it may also be applicable to somewhat
older women who may not have acquired all four serotypes.
Solid organ transplantation is a life-saving modality; however, patients are on life-long
immunosuppression which puts them at increased risk of infections as well as cancers.
Studies have shown a high incidence of HPV infection in transplant recipients ranging from
17.5-45% [4-8]. An evaluation of 105 renal transplant recipients showed that 17.5% patients
were infected with HPV . Another study of 39 renal transplant recipients screened for
HPV showed the presence of HPV in 30.7% of patients, primarily in the cervix .
Therefore, the risk of HPV infection has been estimated to be 17 times greater in renal
transplant recipients than a matched immunocompetent population. Ano-genital neoplasia,
related to HPV, is about 16-20 times more common in transplant recipients [5,6].
Yearly physical examinations of the anogenital area and annual Pap smears are recommended
for transplant recipients . However, there are no data on the immunogenicity of
quadrivalent HPV vaccine in solid organ transplant recipients and no formal recommendations
for vaccination in transplant recipients exist. Given that this is a patient population
that is uniquely susceptible to HPV infection and its sequelae, it is important that vaccine
immunogenicity be studied in transplant recipients.
Endpoint Classification: Safety/Efficacy Study, Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Prevention
The primary outcome will be a 2-fold rise in the type-specific HPV titer for at least one of the four sertypes contained in the vaccine at month 7.
Deepali Kumar, MD
University of Alberta
Canada: Health Canada