Patient description: A 42-year-old healthy woman came to the clinic to have her flu shot in early October. She works in a rehab center and has no underlying disease. It's her first time getting the vaccine this year. She is married for 5 years and uses barrier methods of contraception. Her menstrual cycle is irregular. She does not smoke. She is not on any medications. She exercises regularly for 30 minutes a day at least 5 days a week. She has no history of allergies to any food or drugs. Her past surgical history is significant for tonsillectomy and she is otherwise healthy.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Chronic Lymphocytic Leukemia Small Lymphocytic Lymphoma Patients with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) with active disease. 2. Patients must be age 18 or over at the signing of consent and must understand and voluntarily sign an informed consent. 3. Prior treatment with purine analog based chemotherapy or chemoimmunotherapy. 4. Eastern Cooperative Oncology Group (ECOG)/World Health Organization (WHO) performance status of 0-2. 5. Adequate renal function indicated by serum creatinine less or equal to 2 mg/dl. Adequate hepatic function indicated as total bilirubin less or equal to 2 mg/dl and ALT less or equal to two times the upper limit of normal. 6. Disease free of prior malignancies for 3 years with exception of currently treated basal cell, squamous cell carcinoma of the skin, or carcinoma "in situ" of the cervix or breast. Patients with malignancies with indolent behavior such as prostate cancer treated with radiation or surgery can be enrolled in the study as long as they have a reasonable expectation to have been cured with the treatment modality received. 7. Females of childbearing potential (FCBP) must have a negative serum or urine pregnancy test (sensitivity of at least 50 milli-International unit (mIU/mL) 10-14 days prior to starting lenalidomide. A female of childbearing potential is a sexually mature woman who: 1) has not undergone a hysterectomy or bilateral oophorectomy; or 2) has not been naturally postmenopausal for at least 24 consecutive months (i.e., has had menses at any time in the preceding 24 consecutive months). 8. Continued from #7. FCBP must either commit to continued abstinence from heterosexual intercourse or begin TWO acceptable methods of birth control, one highly effective method and one additional effective method AT THE SAME TIME, at least 28 days before she starts talking lenalidomide. FCBP must also agree to ongoing pregnancy testing. 9. Continued from #8: Men must agree to use a latex condom during sexual contact with a FCBP even if they have had a successful vasectomy. All patients must be counseled at a minimum of every 28 days about pregnancy precautions and risks of fetal exposure. 10. Men must agree not to father a child. They must agree to use a latex condom during sexual contact with females of childbearing potential while participating in the study and for at least 28 days following discontinuation from the study even if he has undergone a vasectomy. They will be warned that sharing study drug is prohibited and will be counseled about pregnancy precautions and potential risks of fetal exposure. They must agree to abstain from donating blood, semen, or sperm during study participation and for at least 28 days after discontinuation from the study. 11. Continued from #10: Counseling about the requirement for latex condom use during sexual contact with females of childbearing potential and the potential risks of fetal exposure must be conducted at a minimum of every 28 days. During counseling, subjects must be reminded not to share study drug and to not donate blood, sperm, or semen (during study participation and for 28 days following discontinuation from the study)  Known sensitivity to lenalidomide or other thalidomide derivatives or rituximab. 2. Documented prolymphocytic leukemia (prolymphocytes more than 55% in the blood). 3. Known positivity for HIV or active hepatitis (B or C). 4. Pregnant or breast feeding females. 5. History of tuberculosis treated within the last five years or recent exposure to tuberculosis. 6. Any serious medical condition, laboratory abnormality, or psychiatric illness that places the subject at unacceptable risk if he/she were to participate in the study. 7. Patients with a recent history of deep vein thrombosis (DVT) or pulmonary embolus (PE), in the six months prior to enrollment are not eligible for this study