For the identified groups of patients (survivors of childhood cancer and youth with sickle cell disease) the investigators want to better understand the barriers to, and facilitators of, HPV vaccination. Through HCP interviews the investigators will also assess both attitudinal and logistical obstacles to HPV vaccination. Some subspecialty HCPs may believe, for instance, that it is the primary care provider's responsibility to vaccinate or they may be unfamiliar with the requirement to enter vaccination data into CHIRP. Also, in some cases HPV vaccine may not be readily available in subspecialty clinic locations and/or subspecialty HCPs may not be Vaccines for Children (VFC) providers. Participants: the investigators will focus on two patient groups: survivors of childhood cancer, which includes children aged 9-21 years who have completed active therapy for cancer and are eligible for vaccination, and sickle cell disease, which includes children aged 9-21 years with a diagnosis of sickle cell disease. The investigators will recruit parents of children aged 9-21 years and older adolescents aged 18-21 years. For pediatric patients, the investigators selected a lower age of 9 years because HPV vaccine is licensed down to 9 years of age, and an upper limit of 21 years, as that is considered the upper bound of adolescence by the American Academy of Pediatrics. For patients 9-17 years of age, only parents will be interviewed by video or phone because parents are the vaccine decision-makers. For patients 18-21 years of age, the investigators will interview both young adults and their parents, because, while the young adult has legal decision-making capacity, in reality, the decision is frequently made jointly by the young adult and parent, and older adolescents are frequently unwilling to go against their parents' wishes. All research procedures will be conducted in English. Participants will be excluded if they have an intellectual disability or severe medical illness such that they are unable to consent or to understand the questions.

Inclusion Criteria:

• Age 9-21 years of age for patients with sickle cell disease or cancer.
• Caregiver of patient with sickle cell disease or cancer.
• Healthcare provider of patient with sickle cell disease or cancer.

Exclusion Criteria:

• n/a

Patients with sickle cell disease or cancer. Caregivers of patients with sickle cell disease or cancer. Healthcare providers of patients with sickle cell disease or cancer.