Sexually transmitted human papillomavirus type 16 (HPV-16) infection is quite common, affecting about one in five adults. HPV-16 is commonly associated with cervical cancer; it is present in about one half of cases. Koutsky and colleagues report on a vaccine against HPV-16 and its efficacy in preventing persistent infection.

The authors enrolled 2,392 women, 16 to 23 years of age, from U.S. college campuses and surrounding communities. Pregnant women, women with previous abnormal Papanicolaou (Pap) smears, and women who had more than five male sexual partners in their lifetime were excluded. At enrollment, subjects underwent thin-layer Pap testing and measurement of serum HPV-16 antibody by radioimmunoassay and enzyme-linked immunosorbent assay. Cervical lavage specimens were collected for testing by polymerase chain reaction. Women with any positive test for HPV infection within the first seven months of enrollment were not included in the analysis. This step led to the exclusion of 510 women (21 percent); 349 enrollees (15 percent) were excluded because of lost follow-up or protocol violations.

Participants were randomized to vaccination with HPV-16 viral capsid particles or placebo at three points: study entry, month 2, and month 6. Seroconversion occurred in 99.7 percent of active vaccine recipients.

None of the active vaccine recipients developed persistent HPV-16 infection during the course of the study. Transient infection (positive HPV-16 testing that reverted to negative at follow-up) was detected in six of the 768 active vaccine recipients. Among the 765 women who received placebo, transient HPV-16 infection was detected in 27 patients and 41 patients developed persistent infection. No persistent HPV-16 infections were detected in the active vaccine group even after inclusion of patients who violated the study protocol. The incidence of adverse effects was similar between the two groups.

The authors concluded that vaccination with HPV-16 capsid particles provided 100 percent protection against persistent infection with this HPV subtype.

editor's note: In a related editorial, Crum notes that cervical cancer is the second leading cause of female cancer deaths worldwide. Many different HPV subtypes are associated with cancer. However, five subtypes account for the majority of cases. If vaccination with the other subtypes is as effective and easy as it was in this trial for HPV-16, widespread vaccination before the age of sexual activity could markedly decrease cervical cancer mortality and in a manner much more cost-effective than the present methods of Pap smear, colposcopy, and cervical surgery.—b.z.