HPV vaccine may be effective in fewer than three doses

Kreimer AR. J Natl Cancer Inst. 2011;doi:10.1093/jnci/djr319.

Issue: October 2011

One and two doses of the HPV 16/18 vaccine were as beneficial as the three-dose regimen 4 years after vaccination, according to data from a recent study.

Aimee R. Kreimer, PhD, of the division of cancer epidemiology and genetics at the National Cancer Institute, NIH, and colleagues used data from the NCI-sponsored Costa Rica Vaccine Trial to determine whether a lower number of doses of the bivalent HPV vaccine (Cervarix, GlaxoSmithKline) were effective. Women in the trial (n=7,466) received either three doses of the vaccine or a control vaccine.

Twenty percent of the women enrolled received fewer than three doses of the vaccine because of factors such as pregnancy and referrals for colposcopy during routine management. During 4 years of follow-up, Kreimer and colleagues compared the frequency of persistent HPV 16 or HPV 18 infection in the HPV and control arms among those who received one or two doses of the vaccine and in women who received all three doses. Women with no follow-up or who were HPV 16 and HPV 18 DNA-positive at the time of enrollment were excluded, resulting in 5,967 women who received three doses, 802 who received two doses and 384 who received one dose.

The level of protection was similar among women receiving one, two and three doses of the vaccine, according to the researchers. Efficacy rates were: 80.9% for three doses (95% CI, 71.1-87.7), 84.1% for two doses (95% CI, 50.2-96.3) and 100% for one dose (95% CI, 66.5-100).

"Our clinical efficacy data provide suggestive evidence that an HPV vaccine program that provides fewer doses to more women could potentially reduce cervical cancer incidence more than a standard three-dose program that uses the same total number of doses but in fewer women," the researchers wrote.

In an accompanying editorial, Cosette Marie Wheeler, PhD, of the department of pathology and department of obstetrics and gynecology at the University of New Mexico, said there is a need for additional, larger studies specifically designed to analyze the efficacy of one, two and three doses of the vaccine for adolescent girls. Due to the high cost of clinical trials, however, phase 4 efficacy studies and population-based surveillance programs may be useful.

"The age-old adage of less is more may apply to HPV vaccination, and if so, the report of Kreimer et al represents an important step on the road to more effective and sustainable cervical cancer prevention programs," Wheeler said.

Cynthia Holland-Hall, MD, MPH

HPV is ubiquitous among sexually active adolescents and young adults, who acquire the infection rapidly after the onset of sexual activity. It was recently reported in the Morbidity and Mortality Weekly Report that the rate of increase in vaccination against HPV is lagging behind those of other adolescent vaccines (CDC. MMWR. 2011; 60;1117-1123). The media continues to disseminate misinformation about the safety of the HPV vaccines, and even pediatric providers are sometimes ill-equipped to respond to patients’ questions and concerns, despite there being no evidence that the vaccines cause serious adverse health effects. For adolescents, who are not major utilizers of pediatric health care, the challenge of completing a three-dose vaccine series is particularly daunting. This study suggests that even two doses of the series may be efficacious in protecting against persistent infection with HPV 16/18. Ideally, the two-dose vaccine series will be studied explicitly to determine its efficacy relative to the three-dose series. In the mean time, we can be encouraged by the possibility that we are offering some degree of protection to all patients in whom we initiate the vaccine series.

– Cynthia Holland-Hall, MD, MPH

Associate professor, of clinical pediatrics, The Ohio State University College of Medicine

Physician, in the section of adolescent health, at Nationwide Children’s Hospital, Columbus, Ohio

Disclosure: Dr. Holland-Hall reports no relevant financial disclosures.

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