**6. Efficacy in clinical trials**

Six major clinical trials enrolling around 44.000 females were conducted to evaluate the efficacy of Cervarix® (2 trials) and Gardasil® (4 trials). Most of the trials included subjects from the age of 15 to 26 years (except for Muñoz *et al*, 24-45 years) with a limited lifetime number of sexual partners (≤4-6, except for Muñoz *et al.*, with no restriction). The sole exclusion criteria were pregnancy and abnormal Pap smears [21, 42-46].

Since cervical cancer is an unethical endpoint for the HPV prophylactic vaccines efficacy evaluation, the clinical trials concentrated on prevention of pre-cancerous high-grade cervical intraepithelial neoplasias (CIN 2 and 3). Results from these trials have shown the high efficacy of the prophylactic vaccines in preventing persistent infection and CIN 2/3 lesions and genital warts for Gardasil® and Cervarix®.

### **6.1. Cervarix®**

The double-blind randomized controlled PATRICIA (PApilloma TRIal against Cancer In young Adults) is the largest Cervarix® vaccine trial performed to date and it was conducted in more than 14 countries from Asia-Pacific, Europe, North America and Latin America. It included over 18.000 healthy women between 15 and 25 years of age with no more than six lifetime sexual partners; these women were enrolled irrespective of their HPV DNA status, HPV serostatus or cytology baseline.

Cervical cytologies and biopsies for 14 oncogenic HPV types were assessed by PCR. The primary endpoint for the vaccine efficacy was the development of CIN 2+ associated with HPV16 or HPV18 and as well non-vaccinated oncogenic HPV types (for cross-protection assessment) [34, 47].

Data from three different cohorts (ATP-E: according to protocol cohort for efficacy vaccinated: n=8093; control: n=8069; TVC: total vaccinated cohort = women receiving at least one dose of the Cervarix®: n=9319; control: n=9325; and TVC-naïve = no evidence of oncogenic HPV infection at baseline vaccinated: n=5822; control: n=5819) over a mean of 34.9 months was analyzed. The efficacy of the vaccine against CIN2/3 lesions associated with HPV16/18 was similarly high (around 98% for CIN2+ and 100% for CIN3+) in the ATP-E and TVC- naïve cohorts. For the TVC group the efficacy of the vaccine against CIN3+ lesions, irrespective of HPV DNA in lesions, was 30%.

### **6.2. Gardasil®**

Both vaccines lead to seroconversion of nearly 100% of the immunized subjects. Cervarix® was shown to sustain relatively stable immunity against HPV16/18 for more than eight years [31]. Subjects immunized with Gardasil® were shown to be consistently seropositive for more than four years for HPV11, HPV6 and HPV16 but a decline in antibody titers was recorded for HPV18 (from 100% to approximately 47%) [32]. However, it cannot be excluded that this observed decline is a result of assay insensitivity. Nevertheless, the protection against HPV18 induced lesions did not decrease suggesting that low levels of anti-HPV18 antibodies are sufficient to confer protection. The Table 3 shows the efficacy of Cervarix® and Gardasil® for

HPV = Human papillomavirus. According to protocol population = women HPV16 or HPV18 DNA negative during the vaccination schedule, that received 3 doses of the vaccine; Per protocol population = participants received 3 doses of vaccine or placebo within 12 months and were seronegative on PCR analysis for HPV6-, HPV-11, HPV-16, or HPV18 at day 1 through 1 month after the third dose.\* Persistent infection correspond to infection detected for ≥6 months. N/A:

**Vaccine efficacy % (95% CI)**


**CIN2 lesions - HPV16/18**

100% N/A − − [33]

100% 100% 100% − [35]

100% 100% 100% − [36]

100% 100% 100% − [37]

100% 100% 100% − [38]

− − 100% 97% [39]

− − 100% 100% [40]

96.6% 90.6% 100% 100% [41]

**CIN3 lesions - HPV16/18**

**Reference**

**HPV 18 persistent\* infection**

different clinical trials followed up for different periods of time.

**Vaccine**

Cervarix®

Gardasil®

not available.

**Years (approximate) after vaccination**

**Cohort**






Per protocol susceptible population

Per protocol susceptible population

Per protocol susceptible population

1.5 According

<sup>3</sup> According

4.5 According

5.5 According

7.3 According

8.4 According

3

3

5

**Table 3.** Cervarix® and Gardasil® efficacy

**HPV16 persistent\* infection**

154 Human Papillomavirus and Related Diseases – From Bench to Bedside A Diagnostic and Preventive Perspective

The randomized, double-blind, placebo-controlled trials FUTURE I and FUTURE II included 18.174 women between 16-26 years of age from 24 different countries from Asia-Pacific, North America, Latin America and Europe. The primary endpoints for the Gardasil® efficacy clinical trial were a) incidence of genital warts, vulvar or vaginal intraepithelial neoplasia or cancer and b) the incidence of cervical intraepithelial neoplasia CIN2/3 and adenocarcinoma *in situ* (AIS) lesions [48, 49]

For the FUTURE II study, which enrolled 12,167 women that were followed for an average of 3 years, Gardasil® efficacy for prevention of HPV-16/18 related CIN3 lesions was 97% in the per-protocol cohort (population negative for 14 HPV types and receiving all the three doses of the vaccine), 95% in the unrestricted susceptible population (population receiving one or more vaccination doses) and 45% in the intention-to-treat cohort (population with or without previous HPV infection). HPV16/11/16/18 related high grade vulvar and vaginal lesions could be prevented with 100% efficacy by vaccination with Gardasil® in the per-protocol, with 95% in the unrestricted susceptible, and with 73% in the intention-to-treat populations. Gardasil® efficacy for prevention of adenocarcinoma *in situ* was 100% in the per-protocol susceptible and unrestricted susceptible population and 28% in the intention-to-treat population. However, one subject in the per-protocol susceptible placebo population developed adenocarcinoma *in situ*, affecting the reliability of the vaccine efficacy in this group [50].

against persistent HPV16 and HPV18 infections as the three doses [51]. What remains unclear

Human Papillomavirus Prophylactic Vaccines and Alternative Strategies for Prevention

http://dx.doi.org/10.5772/55852

157

One surprising finding of the phase II and phase III clinical trials is that both vaccines induce

A recent end-of-study analysis of the Cervarix® PATRICIA clinical trial, performed after 48 months of follow-up, evaluated the cross-protection against non-vaccine HPV types in persistent infection and high grade CIN2+ and CIN3+ lesions. In summary, this analysis reports consistent vaccine efficacy against HPV31, HPV33 and HPV45 for all the end-points [52]

The analysis of combined data from the Gardasil® FUTURE I and FUTURE II clinical trials reveals that vaccination reduced the rate of HPV-31/33/45/52/58 infection, CIN1-3 and AIS. However the reduction of HPV-31/33/45/52/58 related CIN2 lesions was not significant [53] A meta-analysis study suggests that cross-protection efficacy against persistent HPV infection and CIN2 lesions is higher for Cervarix® than for Gardasil®. While Gardasil® can confer protection against the non-vaccine type HPV31, Cervarix® can efficiently protect against HPV 31, HPV 33 and HPV45. This study evaluated comparable populations in different clinical trials that used different methods to identify efficacy endpoints (e.g. genotyping of HPV to deter‐ mine HPV persistent infection). The sensitivity of the methods used in clinical trials and population differences can influence the comparison between Cervarix® and Gardasil®[54]. A sub-analysis of an observer-blind study, performed to allow a direct comparison between Cervarix® and Gardasil®, evaluated cross-protection against non-vaccine HPV types for both vaccines. This study confirmed that both vaccines induce cross-reactive responses against HPV31 and HPV45 but that the responses were initially much lower for the Gardasil® vaccinated group. However, after 24 months the level of humoral responses for HPV31/45 was equally low for both vaccines. The only considerable difference between the vaccines shown in this study is the higher levels of T-cell response with the Cervarix® vaccine. Whether or not

is the duration of protection for the vaccination with fewer doses.

the T cell response is necessary for cross-protection remains unclear [55].

and vaccination of 9 to 26 year old males and females for Gardasil® [57, 58].

degree and durability of cross-protective responses.

**7. Age for HPV vaccination**

**7.1. Preadolescent girls and young women**

All the studies show lower levels of non-vaccine HPV antibody titers compared to the typespecific titers. One possibility to be considered is that the cross-protective responses will wane with time. There are on-going efforts in current phase IV surveillance studies addressing the

Vaccination with Gardasil® or Cervarix® does not lead to clearance of pre-existing HPV infections [56]. Considering the decreasing age of sexual debut in many countries, both vaccines target preadolescent girls and young women. The Advisory Committee on Immuni‐ zation Practices (ACIP) recommend vaccination of females aged 13 to 26 years for Cervarix®

cross-protection against non-vaccine HPV types.

**6.5. Cross-protection**

### **6.3. Cervarix® versus Gardasil®**

After the data from several clinical trials ensuring safety, tolerability and efficacy of the HPV vaccines was published, discussions began about which vaccine should be implemented in public vaccination programs. To make this decision, the cost-effectiveness of the vaccines, potentially influenced by duration of protection, number of doses required for protection and the extend of cross-protection, needed to be evaluated.

It is a difficult and daunting task to directly compare results from the Cervarix® and Gardasil® clinical trials because of a) differences in the study population and cohorts for testing the vaccine efficacy, b) differences in the HPV typing and immunological assays and c) differences in the studies' endpoints.

For this reason, an observer-blind study was designed to directly compare the immunogenicity and safety of both vaccines [23]. In this study, a total of 1106 women aged 18 to 45 years were enrolled and vaccinated either with Gardasil® or Cervarix®. One month after the third vaccination, sera from all the subjects were collected and the presence of neutralizing anti‐ bodies was measured by pseudovirions-based neutralization assay (PBNA). The PBNA showed that all women in both vaccine groups were HPV16 and HPV18 seropositive with the exception of two HPV18 seronegative subjects in the Gardasil® group.

The titers of anti-HPV16 and HPV18 neutralizing antibodies from serum and cervicovaginal secretions induced by Cervarix® were significantly higher than those induced by Gardasil® in all the tested age strata. The frequency of antigen-specific (HPV16 and HPV18) and memory B-cells were also higher in the Cervarix® than in the Gardasil® group [23].

#### **6.4. Dose**

Although both vaccines were licensed as 3-dose administrations over six months, this regime has been questioned and re-evaluated either for cost-effectiveness or for difficulties with administering all the doses within the stipulated time frame.

Recently a comparative analysis between the Costa Rica Vaccine Trial cohort was published where it was suggested that two and maybe even one dose of Cervarix® might be as effective against persistent HPV16 and HPV18 infections as the three doses [51]. What remains unclear is the duration of protection for the vaccination with fewer doses.

#### **6.5. Cross-protection**

For the FUTURE II study, which enrolled 12,167 women that were followed for an average of 3 years, Gardasil® efficacy for prevention of HPV-16/18 related CIN3 lesions was 97% in the per-protocol cohort (population negative for 14 HPV types and receiving all the three doses of the vaccine), 95% in the unrestricted susceptible population (population receiving one or more vaccination doses) and 45% in the intention-to-treat cohort (population with or without previous HPV infection). HPV16/11/16/18 related high grade vulvar and vaginal lesions could be prevented with 100% efficacy by vaccination with Gardasil® in the per-protocol, with 95% in the unrestricted susceptible, and with 73% in the intention-to-treat populations. Gardasil® efficacy for prevention of adenocarcinoma *in situ* was 100% in the per-protocol susceptible and unrestricted susceptible population and 28% in the intention-to-treat population. However, one subject in the per-protocol susceptible placebo population developed adenocarcinoma *in*

156 Human Papillomavirus and Related Diseases – From Bench to Bedside A Diagnostic and Preventive Perspective

After the data from several clinical trials ensuring safety, tolerability and efficacy of the HPV vaccines was published, discussions began about which vaccine should be implemented in public vaccination programs. To make this decision, the cost-effectiveness of the vaccines, potentially influenced by duration of protection, number of doses required for protection and

It is a difficult and daunting task to directly compare results from the Cervarix® and Gardasil® clinical trials because of a) differences in the study population and cohorts for testing the vaccine efficacy, b) differences in the HPV typing and immunological assays and c) differences

For this reason, an observer-blind study was designed to directly compare the immunogenicity and safety of both vaccines [23]. In this study, a total of 1106 women aged 18 to 45 years were enrolled and vaccinated either with Gardasil® or Cervarix®. One month after the third vaccination, sera from all the subjects were collected and the presence of neutralizing anti‐ bodies was measured by pseudovirions-based neutralization assay (PBNA). The PBNA showed that all women in both vaccine groups were HPV16 and HPV18 seropositive with the

The titers of anti-HPV16 and HPV18 neutralizing antibodies from serum and cervicovaginal secretions induced by Cervarix® were significantly higher than those induced by Gardasil® in all the tested age strata. The frequency of antigen-specific (HPV16 and HPV18) and memory

Although both vaccines were licensed as 3-dose administrations over six months, this regime has been questioned and re-evaluated either for cost-effectiveness or for difficulties with

Recently a comparative analysis between the Costa Rica Vaccine Trial cohort was published where it was suggested that two and maybe even one dose of Cervarix® might be as effective

*situ*, affecting the reliability of the vaccine efficacy in this group [50].

exception of two HPV18 seronegative subjects in the Gardasil® group.

B-cells were also higher in the Cervarix® than in the Gardasil® group [23].

administering all the doses within the stipulated time frame.

the extend of cross-protection, needed to be evaluated.

**6.3. Cervarix® versus Gardasil®**

in the studies' endpoints.

**6.4. Dose**

One surprising finding of the phase II and phase III clinical trials is that both vaccines induce cross-protection against non-vaccine HPV types.

A recent end-of-study analysis of the Cervarix® PATRICIA clinical trial, performed after 48 months of follow-up, evaluated the cross-protection against non-vaccine HPV types in persistent infection and high grade CIN2+ and CIN3+ lesions. In summary, this analysis reports consistent vaccine efficacy against HPV31, HPV33 and HPV45 for all the end-points [52]

The analysis of combined data from the Gardasil® FUTURE I and FUTURE II clinical trials reveals that vaccination reduced the rate of HPV-31/33/45/52/58 infection, CIN1-3 and AIS. However the reduction of HPV-31/33/45/52/58 related CIN2 lesions was not significant [53]

A meta-analysis study suggests that cross-protection efficacy against persistent HPV infection and CIN2 lesions is higher for Cervarix® than for Gardasil®. While Gardasil® can confer protection against the non-vaccine type HPV31, Cervarix® can efficiently protect against HPV 31, HPV 33 and HPV45. This study evaluated comparable populations in different clinical trials that used different methods to identify efficacy endpoints (e.g. genotyping of HPV to deter‐ mine HPV persistent infection). The sensitivity of the methods used in clinical trials and population differences can influence the comparison between Cervarix® and Gardasil®[54].

A sub-analysis of an observer-blind study, performed to allow a direct comparison between Cervarix® and Gardasil®, evaluated cross-protection against non-vaccine HPV types for both vaccines. This study confirmed that both vaccines induce cross-reactive responses against HPV31 and HPV45 but that the responses were initially much lower for the Gardasil® vaccinated group. However, after 24 months the level of humoral responses for HPV31/45 was equally low for both vaccines. The only considerable difference between the vaccines shown in this study is the higher levels of T-cell response with the Cervarix® vaccine. Whether or not the T cell response is necessary for cross-protection remains unclear [55].

All the studies show lower levels of non-vaccine HPV antibody titers compared to the typespecific titers. One possibility to be considered is that the cross-protective responses will wane with time. There are on-going efforts in current phase IV surveillance studies addressing the degree and durability of cross-protective responses.
