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HPV Vaccine Gardasil 98% Effective in Preventing HPV-16 or HPV-18 Related Disease, 2 Major Cancer Causing Strains
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"Quadrivalent Vaccine against Human Papillomavirus to Prevent High-Grade Cervical Lesions
The FUTURE II Study Group"
NEJM, May 10, 2007
"....In this ongoing study, subjects were followed for an average of 3 years after the administration of the first dose of vaccine or placebo. When administered to subjects who had not been previously exposed to either HPV-16 or HPV-18, the prophylactic HPV vaccine was highly effective (98%) in preventing HPV-16-related and HPV-18-related cervical intraepithelial neoplasia grade 2 or 3 and adenocarcinoma in situ. Efficacy was lower (44%) for the population of all women who had undergone randomization, which also included subjects who had HPV-16-related or HPV-18-related cervical intraepithelial neoplasia or infection with HPV-16 or HPV-18 before the first injection.... In this population, 1 woman in the vaccine group and 42 women in the placebo group received the diagnosis of cervical intraepithelial neoplasia grade 2 or 3 or cervical adenocarcinoma in situ associated with HPV-16, HPV-18, or both. The single subject whose disease was counted as a case (defined as a consensus diagnosis) of HPV-16-positive cervical intraepithelial neoplasia grade 3 in the vaccine group was positive for HPV-52 at baseline as well as in five histologic specimens collected at the time of diagnosis and treatment. HPV-16 DNA was detected in one histologic specimen but at no other time points.... Prophylactic HPV vaccines must be safe and efficacious in diverse settings because women throughout the world are at risk for cervical cancer. In this trial and in a previous trial,10 no safety concerns among nonpregnant women were identified. Additional data on vaccination during pregnancy are needed. Since women with human immunodeficiency virus infection or other immunosuppressive conditions were not enrolled in our study, future trials will be needed to evaluate safety and efficacy in these populations....These data demonstrate that a quadrivalent HPV-6/11/16/18 vaccine was highly effective in preventing high-grade cervical lesions associated with HPV-16 and HPV-18. Widespread immunization of female children and adolescents may result in a substantial decrease in HPV-16-related and HPV-18-related cervical disease, including cervical cancer."
ABSTRACT
Background Human papillomavirus types 16 (HPV-16) and 18 (HPV-18) cause approximately 70% of cervical cancers worldwide. A phase 3 trial was conducted to evaluate a quadrivalent vaccine against HPV types 6, 11, 16, and 18 (HPV-6/11/16/18) for the prevention of high-grade cervical lesions associated with HPV-16 and HPV-18.
Methods In this randomized, double-blind trial, we assigned 12,167 women between the ages of 15 and 26 years to receive three doses of either HPV-6/11/16/18 vaccine or placebo, administered at day 1, month 2, and month 6. The primary analysis was performed for a per-protocol susceptible population that included 5305 women in the vaccine group and 5260 in the placebo group who had no virologic evidence of infection with HPV-16 or HPV-18 through 1 month after the third dose (month 7). The primary composite end point was cervical intraepithelial neoplasia grade 2 or 3, adenocarcinoma in situ, or cervical cancer related to HPV-16 or HPV-18.
Primary Hypothesis and End Points
The primary hypothesis stated that, as compared with placebo, the vaccine would reduce the incidence of high-grade cervical intraepithelial neoplasia related to HPV-16 or HPV-18 in the per-protocol susceptible population. End-point assignment was based on the blinded consensus diagnosis of at least two pathologists. The primary composite end point was cervical intraepithelial neoplasia grade 2 or 3, adenocarcinoma in situ, or invasive carcinoma of the cervix, with the detection of DNA from HPV-16, HPV-18, or both in one or more of three adjacent sections of the same lesion.9 The evaluations were performed with the use of WHO histologic criteria.11,12
Results
Subjects were followed for an average of 3 years after receiving the first dose of vaccine or placebo. Vaccine efficacy for the prevention of the primary composite end point was 98% (95.89% confidence interval [CI], 86 to 100) in the per-protocol susceptible population and 44% (95% CI, 26 to 58) in an intention-to-treat population of all women who had undergone randomization (those with or without previous infection). The estimated vaccine efficacy against all high-grade cervical lesions, regardless of causal HPV type, in this intention-to-treat population was 17% (95% CI, 1 to 31).
Conclusions In young women who had not been previously infected with HPV-16 or HPV-18, those in the vaccine group had a significantly lower occurrence of high-grade cervical intraepithelial neoplasia related to HPV-16 or HPV-18 than did those in the placebo group. (ClinicalTrials.gov number, NCT00092534 [ClinicalTrials.gov]).
BACKGROUND
Cervical cancer is the second most common cancer in women and the leading cause of cancer-related death in many developing countries.1 Although well-organized programs for Papanicolaou screening have led to a significant decline in mortality from cervical cancer in developed countries,1 such programs are costly2 and have not been effectively implemented in most developing countries.3
Human papillomaviruses (HPVs) cause virtually all cervical cancers, with HPV types 16 (HPV-16) and 18 (HPV-18) responsible for approximately 70%.4 When phase 3 trials of prophylactic HPV vaccines were in the planning stages, the vaccine advisory committee of the Food and Drug Administration (FDA) recommended that these trials be powered to demonstrate efficacy in preventing high-grade cervical lesions that are classified as cervical intraepithelial neoplasia grade 2 or 3,5 a perspective endorsed by the World Health Organization (WHO).6 In this report, we describe the results of a phase 3 trial of a quadrivalent vaccine against HPV types 6, 11, 16, and 18 (HPV-6/11/16/18) designed to assess the prevention of cervical intraepithelial neoplasia grade 2 or 3, adenocarcinoma in situ, and cervical cancer caused by HPV-16 or HPV-18. HPV-6 and HPV-11, which are rarely detected in high-grade cervical lesions, cause the majority of anogenital warts.7,8 A report by Garland et al.9 on vaccine efficacy against external anogenital, vaginal, and cervical lesions associated with HPV types 6, 11, 16, and 18 appears elsewhere in this issue of the Journal.
Study Design
From June 2002 through May 2003, we enrolled 12,167 women between the ages of 15 and 26 years at 90 study sites in 13 countries in our ongoing double-blind, placebo-controlled, randomized trial. The institutional review board at each center approved the protocol; written informed consent was obtained from all subjects. Women were eligible to participate in the study if they were not pregnant, did not report abnormal results on a Papanicolaou smear, and had had a lifetime number of no more than four sex partners. Subjects were asked to use effective contraception during the vaccination period (day 1 through month 7).
The trial, which was called Females United to Unilaterally Reduce Endo/Ectocervical Disease (FUTURE) II, was designed, managed, and analyzed by Merck in conjunction with external academic investigators and members of the external data and safety monitoring board. The academic authors had full access to the data and the analyses and approved the final manuscript. All authors vouch for the completeness and accuracy of the data presented.
Results
A total of 12,707 women attended the enrollment visit. Of these, 12,167 (96%) met the eligibility requirements; of the eligible subjects, 6087 were randomly assigned to receive vaccine and 6080 to receive placebo. Baseline characteristics were similarly distributed between the two groups (Table 1). At baseline, the results of Papanicolaou tests were abnormal for 11.8% of subjects in the vaccine group and 11.1% in the placebo group (Table 1). The most common reason for exclusion from the two prespecified populations for analysis of prophylactic efficacy was PCR-based detection of HPV-16 or HPV-18 DNA or antibodies at baseline (Table 1 and Table 2).
In this ongoing study, subjects were followed for an average of 3 years after the administration of the first dose of vaccine or placebo. In the per-protocol susceptible population, which included 10,565 of 12,167 women who underwent randomization (87%), the vaccine prevented 98% of HPV-16/18-related high-grade cervical lesions (Table 3). In this population, 1 woman in the vaccine group and 42 women in the placebo group received the diagnosis of cervical intraepithelial neoplasia grade 2 or 3 or cervical adenocarcinoma in situ associated with HPV-16, HPV-18, or both. The single subject whose disease was counted as a case (defined as a consensus diagnosis) of HPV-16-positive cervical intraepithelial neoplasia grade 3 in the vaccine group was positive for HPV-52 at baseline as well as in five histologic specimens collected at the time of diagnosis and treatment. HPV-16 DNA was detected in one histologic specimen but at no other time points.
A total of 11,508 of 12,167 women who underwent randomization (95%) were included in the analysis of the unrestricted susceptible population. Vaccine efficacy remained high at 95% (Table 3). Cervical intraepithelial neoplasia grade 2 or 3 or adenocarcinoma in situ developed in 3 subjects in the vaccine group and in 62 in the placebo group. Of note, more than 99% of subjects in this population eventually received the full three-dose regimen.
To provide a preliminary assessment of the effect of quadrivalent vaccine on high-grade cervical disease related to HPV-16 or HPV-18 in a population that included women with and without prevalent cervical intraepithelial neoplasia and infection due to vaccine and nonvaccine HPV types at baseline, we performed an intention-to-treat analysis of all women who had undergone randomization (Figure 1A and Table 3). Vaccine efficacy was 44%, with high-grade cervical disease related to HPV-16 or HPV-18 developing in 83 subjects in the vaccine group and 148 in the placebo group. Most of the cases (defined as consensus diagnoses) that were added to the first intention-to-treat analysis (98%), as compared with those in the unrestricted susceptible population, were high-grade cervical disease caused by HPV-16 or HPV-18 infection that was present before the first injection. Vaccination did not appear to alter the course of cervical lesions related to HPV-16 or HPV-18 or of infection present at the time of randomization (Table 1 of the Supplementary Appendix). Thus, since the percentage of subjects with an end point associated with infection or disease that was prevalent at baseline decreased over time, the incidence of HPV-16-related or HPV-18-related cervical intraepithelial neoplasia grade 2 or 3 and adenocarcinoma in situ in the placebo group continued to increase while the incidence in the vaccine group began to plateau (Figure 1A). In the second intention-to-treat analysis, 219 subjects in the vaccine group and 266 in the placebo group had prevalent or incident high-grade cervical disease due to vaccine or nonvaccine HPV types, representing a reduction of 17% in the vaccine group (Figure 1B and Table 3). None of the women had invasive cervical cancer.
Among women who tested negative for both HPV-16 and HPV-18 at enrollment (4693 in the vaccine group and 4703 in the placebo group), high-grade cervical disease developed in 95 subjects in the vaccine group and in 130 in the placebo group, a reduction of nearly 27% in the vaccine group (95% CI, 4 to 44). Women who were infected with only HPV-16 or HPV-18 appeared to be protected against disease caused by the type of HPV to which they had tested negative. Though the result was not significant, vaccine efficacy for women who tested positive for HPV-16 (773 in the vaccine group and 798 in the placebo group) appeared to be high for cervical intraepithelial neoplasia grade 2 or 3 and adenocarcinoma in situ caused by HPV-18 (no subjects in the vaccine group and 5 in the placebo group). Vaccine efficacy for women who tested positive for HPV-18 (257 subjects in the vaccine group and 253 in the placebo group) also appeared to be high for cervical intraepithelial neoplasia grade 2 or 3 and adenocarcinoma in situ caused by HPV-16 (no subjects in the vaccine group and 2 in the placebo group).
Among the 1512 vaccinated women in the immunogenicity substudy, more than 99% had seroconversion to the relevant vaccine-type HPV. At month 24, of those subjects in each type-specific per-protocol population included in the immunogenicity substudy, 96% of 986 subjects were seropositive for HPV-6, 97% of 987 were seropositive for HPV-11, 99% of 953 were seropositive for HPV-16, and 68% of 1059 were seropositive for HPV-18, as measured in specific neutralizing antibodies. Although the percentage of women in the vaccine group who maintained detectable levels of HPV-18 antibodies was lower than the percentage with HPV-16 antibodies, the efficacy for prevention of HPV-18-related high-grade lesions was maintained at 100% through follow-up in the unrestricted susceptible population (Table 3).
There were relatively few side effects of vaccination. The proportion of subjects who reported one or more injection-site adverse events was higher in the vaccine group than in the placebo group (84.4% vs. 77.9%), with the most common event being injection-site pain (risk difference, 6.5 percentage points; 95% CI, 1.4 to 11.7) (Table 4). One subject in the placebo group discontinued participation owing to a serious injection-related adverse event (hypersensitivity). The proportions of women reporting serious adverse events were similar in the two treatment groups. (All systemic and serious adverse events, categorized by organ system and treatment group, are provided in Tables 5 and 6 of the Supplementary Appendix.) Within these categories, there were nominally significant differences in the percentages of subjects in the vaccine group and the placebo group who reported seasonal allergies (10 in the vaccine group and 2 in the placebo group [risk difference, 1.8; 95% CI, 0.3 to 3.7]) and neck pain (2 in the vaccine group and 10 in the placebo group [risk difference, -1.8; 95% CI, -3.7 to -0.3]). No multiplicity adjustments were made for these comparisons. Adverse-event profiles were generally similar for women with and without antibodies to one or more of the vaccine-related HPV types at enrollment.
Pregnancy was reported in 1053 subjects in the vaccine group and 1106 in the placebo group. For all phase 3 trials of the quadrivalent vaccine combined (Table 2 of the Supplementary Appendix), 1396 subjects in the vaccine group (13%) and 1436 in the placebo group (16%) had become pregnant, and outcomes were available for approximately 82%. The proportions of women with live births, difficulties with delivery, spontaneous abortions, and late fetal deaths were similar in the two study groups. Congenital anomalies were reported for 41 infants and 6 fetuses (25 in the vaccine group and 22 in the placebo group) (Table 3 of the Supplementary Appendix). A review by an external specialist who was unaware of study-group assignments concluded that the types of anomalies observed were diverse and consistent with those generally seen in young women.16
Further analyses were done to evaluate pregnancies with an estimated date of conception either within 30 days after any vaccination or more than 30 days after any vaccination (Table 4 of the Supplementary Appendix). For pregnancies with an estimated date of conception within 30 days after any vaccination, 19 of 112 in the vaccine group and 26 of 115 in the placebo group resulted in a spontaneous abortion (risk difference, -5.6; 95% CI, -16.1 to 4.8). Of the live-born infants, five were found to have a congenital anomaly (five in the vaccine group and none in the placebo group [risk difference, 4.5; 95% CI, 1.1 to 10.1]). The congenital anomalies observed in these five infants were relatively common and pathogenetically unrelated, suggesting different causes. For pregnancies with an estimated date of conception of more than 30 days after any vaccination, 266 of 1198 in the vaccine group and 283 of 1218 in the placebo group resulted in a spontaneous abortion (risk difference, -1.0; 95% CI, -4.4 to 2.3). A total of 20 infants or fetuses whose mothers were in the vaccine group and 22 whose mothers were in the placebo group were found to have a congenital anomaly (risk difference, -0.1; 95% CI, -1.2 to 1.0).
Discussion
When administered to subjects who had not been previously exposed to either HPV-16 or HPV-18, the prophylactic HPV vaccine was highly effective (98%) in preventing HPV-16-related and HPV-18-related cervical intraepithelial neoplasia grade 2 or 3 and adenocarcinoma in situ. Efficacy was lower (44%) for the population of all women who had undergone randomization, which also included subjects who had HPV-16-related or HPV-18-related cervical intraepithelial neoplasia or infection with HPV-16 or HPV-18 before the first injection. Although prevention of invasive cervical cancer is the main goal of prophylactic HPV vaccination, it is ethically unacceptable to use invasive cancer as the end point in efficacy trials. Cervical intraepithelial neoplasia grade 3 and adenocarcinoma in situ,12 which the International Federation of Obstetrics and Gynecology classifies as stage 0 noninvasive cervical cancers,17 are clinically important outcomes because they are likely to persist18,19,20 and may become invasive without treatment. Although a histologic diagnosis of cervical intraepithelial neoplasia grade 2 is less reproducible and spontaneous regression is more common than for grade 3,19,20 this lesion is also considered to be high grade.12
We took several steps to enhance accuracy, reproducibility, and generalizability of our findings. To ensure high sensitivity for histologic end points, colposcopists were instructed to biopsy all discrete abnormal areas; for high specificity, HPV-16 and HPV-18 DNA had to be detected in tissue sections. Histologic diagnoses were determined by a panel of expert gynecologic pathologists who were unaware of other clinical and laboratory data. Generalizability was enhanced by enrolling women from both developed and developing nations and by using standard Papanicolaou screening and management algorithms.21,22 Prophylactic vaccine efficacy was high for all four geographic regions and for all ethnic or racial groups and was similar to efficacy estimates from phase 2 trials of HPV-16 and HPV-18 infection,10,23 indicating the robustness of our findings.
The mean length of follow-up in this study was 3 years after administration of the first dose of vaccine or placebo. Within this interval, 42 subjects in the placebo group who were included in the per-protocol analysis became infected, and incident high-grade cervical disease related to HPV-16 or HPV-18 developed. As others have reported,24,25,26,27,28 the time from HPV infection to the development of a high-grade cervical lesion is often less than 24 months. These findings suggest that widespread immunization of female adolescents and young women could lead to reductions in HPV-16-related and HPV-18-related high-grade lesions that would be apparent within years, rather than decades.
Although follow-up was relatively short in duration, three previous phase 2 trials of prophylactic HPV recombinant vaccines included 4 to 5 years of follow-up28,29,30 and found no evidence of waning immunity or decreased efficacy for prevention of infection or persistent shedding of virus. Durability of vaccine-induced protection beyond 5 years is unknown. An antigen challenge of quadrivalent HPV-6/11/16/18 vaccine was shown to stimulate an anamnestic response, the hallmark of a vaccine that offers long-lasting protection.31 The planned 15-year follow-up of vaccinated subjects in northern Europe32 should provide essential information on the durability of protection.
Implementation of public health measures is challenging, owing to difficulties in maintaining compliance and to the heterogeneity of target populations. In this study, subjects were encouraged to comply with the three-dose vaccination regimen of administration at day 1, month 2, and month 6; however, subjects were not eliminated from the study if they deviated from this regimen. Analysis of the unrestricted susceptible population showed a high efficacy (95%), indicating that there is flexibility around the suggested regimen. Of note, it is likely that protective antibodies developed in some vaccinated women before they had received three doses, since infection with HPV-16 or HPV-18 before or within 1 month after receiving all three injections added 17 of 20 new cases in the placebo group and only 2 new cases in the vaccine group. On the other hand, there was no clear evidence that vaccination altered the course of HPV-16 or HPV-18 infection that was present before administration of the first vaccine dose.
It is likely that the population of women with prevalent HPV-16 or HPV-18 infection at trial entry was enriched for high-grade disease because high-grade lesions are more likely to persist than are low-grade lesions and because most HPV infections are transient.33 Speculation that elimination of HPV-16 and HPV-18 will open a niche for other high-risk viruses is not supported by the literature. Young women are often infected with multiple high-risk HPV types, and the risk of new infection is greater for women who are infected with one or more HPV types than for uninfected women.34,35,36,37 In addition, levels of viral DNA in clinical specimens may be higher for one HPV type when there is coinfection with another type.38
The quadrivalent vaccine is prophylactic, not therapeutic. Even in the setting of high vaccine coverage, routine screening for cervical cancer will be necessary to detect and treat disease caused by HPV-16 or HPV-18 infections acquired before vaccination and by other carcinogenic HPV types.
Prophylactic HPV vaccines must be safe and efficacious in diverse settings because women throughout the world are at risk for cervical cancer. In this trial and in a previous trial,10 no safety concerns among nonpregnant women were identified. Additional data on vaccination during pregnancy are needed. Since women with human immunodeficiency virus infection or other immunosuppressive conditions were not enrolled in our study, future trials will be needed to evaluate safety and efficacy in these populations.
These data demonstrate that a quadrivalent HPV-6/11/16/18 vaccine was highly effective in preventing high-grade cervical lesions associated with HPV-16 and HPV-18. Widespread immunization of female children and adolescents may result in a substantial decrease in HPV-16-related and HPV-18-related cervical disease, including cervical cancer.
Supported by Merck.
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