Grading of Recommendations Assessment, Development and Evaluation (GRADE) of a 2-dose schedule for human papillomavirus (HPV) vaccination

Introduction

Three HPV vaccines are licensed for use in the United States as a 3-dose series: quadrivalent and 9-valent HPV vaccines (4vHPV and 9vHPV, Gardasil and Gardasil 9, Merck and Co, Inc., Whitehouse Station, NJ)12 and bivalent HPV vaccine (2vHPV, Cervarix, GlaxoSmithKline, Rixensart, Belgium).3 In October 2016, 9vHPV was approved for use in a 2-dose series for girls and boys initiating the vaccination series at ages 9 through 14 years. Grading of Recommendations Assessment, Development and Evaluation (GRADE) was adopted by the Advisory Committee on Immunization Practices (ACIP) in 2011,4 and a 2-dose schedule for HPV vaccine was considered using GRADE. The main policy question was, “Should 2 doses of any HPV vaccine given 6–12 months apart be recommended routinely for 9 through 14 year-olds?” Factors considered in determining the recommendation included benefits and harm, GRADE evidence type, values and preferences, and health economic analyses.

Methods for GRADE

Scientific literature was searched from January 2006 through June 2016 using the PubMed database and ClinicalTrials.gov. The medical subject headings (MeSH) searched were Papillomavirus Vaccines, including all subheadings, with no limitations except human subjects. Text word searches were performed on additional terms, including HPV vaccine, impact, effective, dose, and doses. Studies were included if the population was adolescents (any gender) aged 9–14 years; intervention was administration of 2 doses of any HPV vaccine separated by 6 or more months (±4 weeks); comparison was 3 doses of HPV vaccine among young adults within the age group (15–26 years) in which efficacy was demonstrated in clinical trials; and outcomes were primary data on HPV-associated health outcomes.

The draft policy note based on the ACIP recommendation was shared with ACIP voting members and revisions were made based in part on their feedback. The CDC Director approved a decision memo outlining the recommendation prior to publication of the policy note. The opinions of individual members of ACIP might not be fully reflected in this document, as the guideline represents the position of CDC based on the ACIP recommendation to the CDC director and is not a consensus document. The Work Group continues to review data as they become available, and considers any needed policy changes.

Results

Benefits considered critical outcomes in GRADE were prevention of cervical precancers and cancers, oropharyngeal cancer, anal cancer, vaginal/vulvar cancer, and penile cancers (Table 1). Additional important outcomes included HPV infections and anogenital warts/condyloma. Immunogenicity was considered a surrogate marker for prevention of important and critical outcomes, when immunobridging studies were available comparing immunogenicity in the group of interest (i.e., boys or girls aged 9 through 14 years) with a comparison group in which efficacy has been demonstrated in clinical trials (i.e., women aged 15 or 16 through 26 years).

For 9vHPV, one immunobridging study was identified that was also the basis of the FDA decision on 2-dose approval;5 for 4vHPV, two immunobridging studies were identified67; and for 2vHPV, four immunogenicity studies were identified (Table 2).891011 Included data showed high seroconversion rates among all cohorts and non-inferior geometric mean antibody titers (GMTs) for all HPV vaccine types in boys and girls receiving 2-dose schedules compared with groups in which efficacy was demonstrated in clinical trials. (Table 3). These studies received a final GRADE evidence type of 3. (Table 4) Same-age comparisons of seroconversion rates and GMTs among boys and girls receiving a 2-dose schedule compared with a 3-dose schedule were not included in GRADE but are shown as supplemental data (Table 5).

Overall GRADE evidence type was 3 (Table 6). Favorable safety profiles for HPV vaccines have been well-established,1213 and no data suggest that adverse events increase with a 2-dose schedule compared with a 3-dose schedule. When benefits are similar and potential for adverse events is lower, then the balance of benefits over harms is greater.

Considerations for formulating recommendations for a 2-dose schedule of HPV vaccine included the following key factors: balance of benefits over harms, GRADE evidence type, values and preferences, and cost-effectiveness considerations (Table 7).

Table 1: Important and critical outcomes related to HPV vaccination

Table 1 Footnotes
_{*No data available for dosing interval or age range specified in policy question
^†No data available on these HPV-associated outcomes}

Table 2. Characteristics of included studies

References in this table:567891011

Table 2 Footnotes
_{^a NCT 1984697, funded by Merck; results presented publicly at ACIP in February 2016
^b NCT 00501137, funded by Ministries of Health in British Columbia, Nova Scotia, and Quebec (Laboratory testing: Merck)
^c NCT 01717118, funded by Ministry of Health in Mexico and National Institute of Public Health in Mexico (Laboratory testing: Merck)
^d NCT 00541970, funded by GlaxoSmithKline
e NCT 01381575, funded by GlaxoSmithKline
^f NCT 01717118, funded by Ministry of Health in Mexico (Laboratory testing: GlaxoSmithKline)
^g Specimens from NCT 00541970, NCT 00196924, NCT 00196937, funded by GlaxoSmithKline}

GMTs, Geometric Mean Titers; M, months after dose 1; NCT, National Clinical Trial number

Table 3. Included data, immunogenicity

GMTs, Geometric Mean Titers; M, months after dose 1

Table 4. Type of evidence

Table 4 Footnotes
_{^a Strength of association, dose-response, plausible residual confounding, publication bias
^b Not downgraded for in-directness since immunobridging studies use a comparison group in which clinical efficacy has been established}

Obs, Observational

Table 5. Supplemental data, immunogenicity

GMTs, Geometric Mean Titers; M, months after dose 1

Table 6. Summary of evidence for a 2-dose schedule of HPV vaccine

Table 7: Considerations for formulating recommendations for a 2-dose schedule of HPV vaccine

Summary

After reviewing the available data, including the result of the GRADE analysis, ACIP voted in October 2016 to recommend a 2-dose schedule of HPV vaccine for girls and boys who initiate the vaccination series at ages 9 through 14 years (Category A recommendation). See Use of a 2-Dose Schedule for Human Papillomavirus Vaccination — Updated Recommendations of the Advisory Committee on Immunization Practices.14