DNA vaccines, which are small pieces of DNA also known as plasmids, have several advantages over traditional vaccines such as live attenuated virus and recombinant protein-based vaccines. DNA vaccines appear to be well tolerated in humans. Therefore, the investigators have developed our DNA vaccine, VGX-3100, to include plasmids targeting E6 and E7 proteins of both HPV subtypes 16 and 18. The investigators have chosen to deliver our candidate vaccines via electroporation (EP) using the CELLECTRA constant current device to deliver a small electric charge following intramuscular (IM) injection, since animal studies have shown that this delivery method increases the immune response to our DNA vaccine leading to a decrease in the size of tumors caused by HPV 16 and 18. In study HPV-001, the vaccine was given to subjects with a history of CIN 2 and 3 who had been previously treated by surgery. This study is proposed to vaccinate the same subjects with a fourth dose of the VGX-3100 to determine the safety and immune response.

Inclusion Criteria:

1. Written informed consent in accordance with institutional guidelines;
2. Successful enrollment in and completion of all study procedures and follow-up in study HPV-001.
3. Female 18-46 years of age;
4. Post surgical (including LEEP and conization) or ablative treatment and a diagnosis of CIN 2 or 3, while under physician care as per ASCCP guidelines (Appendix C);
5. Normal ECG and CPK, as judged by Grade 0-1 as per Toxicity Grading Scale for Healthy Adults (Appendix B) done up to 30 days prior to administration of study treatment;
6. Body mass index (BMI) ≤30 kg/m2;
7. Women of child-bearing potential (WOCBP) agree to remain sexually abstinent, use medically effective contraception (oral contraception, barrier methods, spermicide, etc), or have a partner who is sterile (i.e., vasectomy) from enrollment to study discharge;
8. Able and willing to comply with all study procedures.

Exclusion Criteria:

1. Active infection with herpes simplex virus (HSV);
2. Pregnant or breast feeding subjects;
3. Any concurrent condition requiring the continued use of systemic or topical steroids (excluding inhaled and eye drop-containing corticosteroids) or the use of immunosuppressive agents. All other corticosteroids must be discontinued > 4 weeks prior to Day 1 of treatment;
4. Administration of any blood product within 3 months of enrollment;
5. Administration of any vaccine within 6 weeks of enrollment;
6. Patient is currently participating or has participated in a study with an investigational compound or device other than VGX-3100 within 30 days of signing informed consent;
7. Metal implants at the site of injection;
8. Active drug or alcohol use or dependence that, in the opinion of the investigator, would interfere with adherence to study requirements;
9. Prisoners or subjects who are compulsorily detained (involuntarily incarcerated) for treatment of either a psychiatric or physical (i.e. infections disease) illness must not be enrolled into this study;
10. Any other conditions judged by the investigator that would limit the evaluation of a subject.