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 \[1\]. 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 \[2\].

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 months \[2\].

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) \[3\]. 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 \[15\]. 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 \[16\]. 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 \[5\]. Another study of 39 renal transplant recipients screened for HPV showed the presence of HPV in 30.7% of patients, primarily in the cervix \[6\]. 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 \[9\]. 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.