HPV Vaccine Not Effective Therapeutically

Although vaccines are valued primarily for their protective ability, some of them may also enhance the body’s immune response to a preexisting infection. Infection with human papillomavirus (HPV) type 16 or 18, although usually spontaneously cleared, can lead to cervical cancer if persistent. Could an HPV-16/18 vaccine provide adequate immune stimulation to accelerate clearance of an HPV-16 or HPV-18 infection? Investigators addressed this question as part of a larger, ongoing, community-based, randomized trial of a bivalent HPV-16/18 viruslike particle vaccine, conducted in Costa Rica. (Two of the investigators are named inventors on HPV vaccine patents; a third is employed by the manufacturer of the vaccine involved in this trial.)

Recruited between June 2004 and December 2005, the 2189 participants (healthy women aged 18–25) were randomized to receive three doses of either the bivalent HPV vaccine or hepatitis A vaccine. All were positive for HPV DNA at enrollment, had ≥6 months of follow-up, and had follow-up HPV DNA results.

Among the women with HPV-16, HPV-18, or combined HPV-16/18 infection, HPV clearance rates at 6 months and 12 months were similar between the HPV vaccine group and the control group for each HPV type individually and for dual infection. Additionally, no significant differences were noted in relation to HPV-16/18 antibody titers or viral load, or for HPV types other than 16 or 18.