So now that HPV vaccination is recommended for young girls and boys, is the three-series vaccine being completed? Apparently not, says the CDC. Recently the CDC reported that only 32 percent of US females ages 13 to 17 received the complete three-dose series, so what happened to the other 68 percent? Both Gardasil and Cervarix are currently three-dose regimens with mandatory vaccination in Virginia and Washington, DC.
Data from studies in Costa Rica in which a subpopulation of women received only two doses of the vaccine reveals that responses with two doses of Cervarix are "almost as good as with three doses," said Dr. Rick Haupt, head of adult clinical vaccine research at Merck. However, the only data available is from a four-year follow-up study with a small number of participants. This does not provide insight into the duration of protection.
While GlaxoSmithKline (GSK) has no plans of developing a two-dose indication, Merck is in the developmental phase of V503, which will offer protection against five HPV causing genotypes. The late-stage human trial has been delayed by one year due to lack of HPV-infected patients who were given Gardasil, which raises the question: Is there a need to protect against the added three genotypes?
During this trial, they will compare V503 to the current vaccine, Gardasil. If approved, patients previously vaccinated with Gardasil will not need to undergo re-vaccination with V503, though the new vaccine would be given instead of Gardasil should V503 provide the same protection from HPV 16 and 18.
Unfortunately, I was unable to locate sufficient data on male vaccination rates. However, this is probably due to the recent approval for boys and men less than one year ago, and data has yet to be compiled and evaluated. It is difficult to say what effect the incomplete vaccination regimen will have on HPV-related male and female cancers -- only time will tell.
Michelle Bragazzi talked about the lack of compliance in a previous blog. Do you feel a two-dose vaccine would be beneficial to help increase the compliance rate or do we need to increase education?